How Sensitive is Earth's Climate?

The Rate of Change: September 14, 2019

This is the third part in a series breaking down the fundamentals of climate science. Here’s Part 1 and Part 2.


To predict how much the world is going to warm in the future, one of the key numbers to understand is Earth’s climate sensitivity. This is the answer to the question: how much will Earth’s temperature rise if we double carbon dioxide levels?

It turns out that this question is as old as the field of climate science. In 1896, the Nobel Prize winning Swedish chemist Svante Arrhenius took a creative approach to solving this problem. By cleverly reinterpreting data on the intensity of moonlight, Arrhenius was able to make the first modern prediction of Earth’s climate sensitivity. (If you’re interested in how he did this, here’s an in-depth video.)

Arrhenius’s answer — 5 to 6 ℃ — is on the high end, compared to our current understanding. Today climate scientists predict this number to be between 1.5 and 4.5 ℃. But the fact that Arrhenius was even in the right ballpark is impressive, given that he was working with indirect data, had to fill in many gaps in the theory, and spent an entire year crunching the numbers by hand!

By the time Arrhenius carried out his calculation, it was well known that carbon dioxide was a greenhouse gas (a fact that we owe to Eunice Newton Foote, although typically credited to John Tyndall). This was the basis for his work, which he combined with the then brand-new theory of heat.

However, Arrhenius wasn’t particularly concerned about global warming. His main motivation was to understand why the ice ages happened. By extrapolating forwards from 1896, Arrhenius worked out that it would take thousands of years for humans to double carbon dioxide levels.

Which was a perfectly reasonable prediction to make in 1896, unless of course humans somehow managed to exponentially increase their carbon emissions.

Well… we all know how that turned out.

Today, we’re in the process of actually conducting Arrhenius’s alarming thought experiment. We’re nearly halfway to a CO₂ doubling compared to pre-industrial levels, and our carbon emissions are accelerating.

So it’s easy to see why Earth’s climate sensitivity is an important number to understand. It helps us understand the future.

We don’t really know where our carbon dioxide levels will end up, that depends on the extent to which climate action succeeds. But Earth’s climate sensitivity lets us predict how much warming we can expect to see in different possible climate futures.

A First Attempt at Calculating Earth’s Climate Sensitivity

So let’s take a stab at cooking up Earth’s climate sensitivity. To do this, we’re going to need a few ingredients.

Take One Part Sunlight

First, we need to know how much sunlight a patch of Earth receives. We’ve encountered this number in previous newsletters — it’s approximately 240 Watts per square meter. We can call this number our incoming energy flow.

The standard term for this quantity is ‘energy flux’. Energy flux = energy / area / time, or the amount of energy absorbed or radiated by 1 square meter of a planet’s surface in 1 second.

This means that one square meter of our planet receives 240 Watts of solar power, on average. I say on average because, of course, day is brighter than night, sunlight is more intense at the equator than at the poles, days are longer in summer than in winter, and so on. This number averages over all these variations.

Also, nearly a third of Earth’s incoming sunlight reflects off stuff like clouds and glaciers — this is known as our albedo (Latin for ‘whiteness’). The number above also takes this into account.

Take An Equal Part Heat

The higher the temperature of any object, the more energy it radiates in the form of heat. In an earlier post, we saw how you can work out a planet’s temperature by balancing the solar energy it receives with the heat that it radiates.

Through this simple balance, we were able to get surprisingly good predictions for the temperature of Mercury and Mars. However, this model falls short for Earth and Venus, because it doesn’t account for the greenhouse effect.

Stick in a Thermometer

To account for the greenhouse effect, we’ll need to know the actual temperature of our planet. Our average temperature is about 15 ℃ (59 ℉), or 288 Kelvin. Once again, this is averaged over the globe, over the seasons, and over day and night.

Yes, we’re leaving out a lot of detail here, but you have to start somewhere. When building a scientific model, there’s always a trade-off between simplicity and detail, and we’re aiming for extreme simplicity here.

The technical term for this type of climate model is a zero-dimensional energy balance model — zero dimensional because we’re only considering global averages, and ignoring the variation at different points on the Earth. The next step up in complexity is a one-dimensional energy balance model, which considers how sunlight, temperature, and ice cover varies with latitude.

Mix in a bunch of CO₂

Finally, we want to understand what happens when we double CO₂. In previous posts, we’ve seen how adding carbon dioxide to the atmosphere increases Earth’s energy imbalance.

Let’s make this quantitative. The IPCC tells us that doubling carbon dioxide will increase Earth’s energy imbalance by 3.7 W/m². This number comes from detailed calculations of how a CO₂ molecule absorbs heat.

You can think of this number as simply being added to our incoming energy flow. To understand what this number means, notice that 3.7 W/m² is about 1.6% of our incoming solar energy flow. So doubling carbon dioxide would have a similar effect on Earth’s temperature as instead making the Sun 1.6 percent brighter.

The technical jargon for this additional energy imbalance is radiative forcing. So climate scientists might say something like “the radiative forcing due to a doubling of CO2 is 3.7 W/m²”.

Now that we have all the ingredients, let’s get cooking.

Set to 288 Kelvin and Bake

Now that we’ve gathered all the pieces that we need, let’s put them together.

Rather than just telling you how this works, I think it’ll be more interesting for you to do it yourself. So I’ve put together an interactive essay that walks you through building a simplified climate model.

It’s called Climate Toy. I hope you find it interesting!

Climate Sensitivity

Feel free to drop me a line with your feedback. Did you find this helpful or instructive? Was it confusing? Would you like to see more stuff like this in future? I’d love to hear what you think.


Recent Climate News

You might have heard that Jonathan Franzen published a piece in the New Yorker arguing that a climate apocalypse is inevitable, and that we should stop pretending that we can avert it, and instead focus on taking more local actions.

Here are my 3 favorite responses to this piece:

  • Ula Chrobak at Popular Science wrote an excellent critique of what the piece gets wrong on climate science and policy.

  • Mary Heglar wrote a powerful, thoughtful, and poetic response: Home is always worth it.

  • Kate Marvel wrote an excellent piece on how understanding climate change changes it from a foregone conclusion to a choice.

Trevor Noah asked Greta Thunberg what people can do to act on climate change. Here’s her brilliant response:

“If I were to choose one thing everyone would do, it would be to inform yourself, and to try to understand the situation, and to try to push for a political movement that doesn’t exist. Because the politics needed to “fix this” doesn’t exist today. I think what we should do as individuals is to use the power of democracy to make our voices heard, and to make sure that the people in power actually can not continue to ignore this.”

NYT put together a phenomenal visual explainer showing the extent of the flooding along in the US Midwest and South.

Visualizing the world’s addiction to plastic bottles. This page opens with a gut punch of an animation. The image below, from the article, visualized a years worth of plastic bottles sold next to the tallest building in the world.

TIME highlights 15 women leading the fight against climate change

We need systemic changes that will reduce everyone’s carbon footprint, whether or not they care.” Michael Mann on how lifestyle changes aren’t enough.

The Washington Post has a great infographic-rich series on the places that have already warmed by over two degrees Celsius.

The UN rights chief on climate change: “The world has never seen a threat to human rights of this scope

If carbon dioxide hits a new high every year, why isn’t every year hotter than the last?

A map of how every part of the world has warmed – and could continue to warm.

The Trump adviser who tried to create a White House panel to attack climate science is leaving the administration.

“There are 118 elements on the periodic table. An iPhone contains about 75 of them.” I thought this was a fascinating piece by Maddie Stone on the challenges of recycling electronics.

The US is planning to open nearly 200 fossil-fuel power plants. What’s worse, the article concludes that many of these plants will be more expensive than renewable alternatives.

“An analysis by the Rocky Mountain Institute published Monday looked at 88 gas-fired power plants scheduled to begin operation by 2025. They would emit 100 million tons of carbon dioxide a year – equivalent to 5% of current annual emissions from the U.S. power sector. 

The institute calculated the cost of producing a megawatt-hour of electricity of a clean energy portfolio in each state that would provide the same level of power reliability as a gas plant. It determined that building clean energy alternatives would cost less than 90% of the proposed 88 plants.”

Read more.

“The mountain peak known to Swedes as their country’s highest can no longer lay claim to the title due to global heating”

Via Brad Plumer: Why did India’s devastating Cyclone Fani kill only 40 people — not 10,000?

“Democratic presidential candidates recently spoke of the need to address the adverse effects of global warming on poor and marginalized communities.”

Another blow for the future of corals. By Ed Yong in the Atlantic.

Shlesinger and his colleague Yossi Loya have found that three common coral species in the Red Sea have lost their rhythm. Their timing is off; their unison is breaking. Rather than releasing a majestic unified blizzard of eggs and sperm at precise moments, they now spawn in pathetic, erratic drizzles across weeks and months. “It doesn’t look promising for those species,” Shlesinger says.

“This study is heartbreaking,” says Shayle Matsuda of the Hawaii Institute of Marine Biology. “This is something we’ve all worried might be true.”

Read more.

Global heating made Hurricane Dorian bigger, wetter – and more deadly

Here are a number of highly rated organizations providing aid and relief in the aftermath of Hurricane Dorian.

Hurricane Dorian may have caused a critically endangered bird to go extinct.

The increasing concentration of carbon dioxide in our atmosphere is making our food more sugary and less nutritious.

Climate misinformation may be thriving on YouTube, a social scientist warns

Are we overestimating how much trees will help fight climate change?

Global 5G wireless networks threaten weather forecasts

New research reveals the loss of forest elephants damages the carbon-storage capacity of the central African forests in which they live

A deeply reported multi-part series on Baltimore’s Climate Divide — how the impact of heating is being felt disproportionately by its most vulnerable residents.

What 500,000 Americans hit by floods can teach us about fighting climate change

To fight global warming, think more about systems than about what you consume. Bill McKibben reviews Tattiana Schlossberg’s new book in the New York Times.

That’s all for this week. See you next time! If you found this newsletter informative or helpful, consider recommending it to a friend. It really helps get the word out. If someone forwarded this email to you, you can subscribe using the button below.

Amazon Fires & Climate Rage

The Rate of Change: August 26, 2019

Understanding the Amazon Fires

This New York Times piece is the best explainer I’ve read on the extent of the fires currently burning in the Amazon Rainforest. It places this August’s fires in the context of the previous decade.

Image: NYT. Description: A map illustrating the extent of fires burning in August in the Brazilian Amazon.

In the years following 2005, there was a very significant reduction in deforestation in Brazil’s Amazon, as a result of environmental protection policies.

Image: NYT. Description: A graph of annual deforestation in the Brazilian Amazon. The numbers show large spikes up to 10,000 square miles in the 1990s and early 2000s, followed by a significant reduction post 2005.

However, in recent years Brazil’s deforestation numbers are on the rise again. Herton Escobar reports in Science Magazine:

“Recent data have clearly shown that deforestation in Brazil is on the rise. From January through the end of July, 6800 square kilometers [2625 square miles] were cleared, according to INPE [Brazil’s National Institute for Space Research], 50% more than in the same period last year. But Bolsonaro called the data “a lie” and had INPE’s director, physicist Ricardo Galvão, fired in early August.”

Julia Rosen at LA Times covered the consequences of losing rainforest area in the Amazon.

James Temple at MIT Technology Review explores whetherdeforestation will push the world’s largest rainforest to a tipping point, where spiraling feedback effects convert much of the forest into savannah”.

The reasoning behind the rainforest tipping point idea goes like this. Although you may think that clouds from afar bring rain to forests, we now know that the Amazon rainforest produces half of its own rainfall. The way it works is that trees suck up water, which evaporates through leaves, seeding new clouds that rain over the forest. Through this cycle, trees in the Amazon can recycle the water brought in by clouds from the Atlantic five to six times over.

In fact, you can even see this process.

Image: NASA Earth Observatory (Public Domain) Via Wikimedia. Click through for image description.

The picture above shows the Amazon during the dry season. The tiny dew-like white spots are very likely clouds created by the process of ‘evapotranspiration’ — they’re the rain clouds that the forest creates. (You can read more about this remarkable process here and here.)

By deforesting the Amazon, among other things, we reduce the forests ability to create rain. The difference can be as high as nearly 50 centimeters (~19 inches) of rain per year, which is nearly a quarter of the annual rainfall, or about an hour of heavy rain per week.

Some scientists argue that this can lead to a vicious cycle where at a certain level of deforestation, the rainforest can no longer produce enough rain to sustain the habitat, and the land converts from forest to savanna.

Minute Earth did a fantastic job of illustrating and explaining this feedback loop, in a video that also highlights the value of indigenous knowledge.

Here’s a remarkable visualization of the carbon store in the Amazon rainforest, by Greg Fiske at Woods Hole Research Center.

Forests as mountains by @greg.fiske for @WoodsHoleResearchCenter. This map shows aboveground forest carbon located in the Amazon. It presents the biomass as 3D elevation surface, so the higher the "mountain," the more carbon is stored within that area.
The Amazon has lost more than 800,000 square km of forest—an area equivalent to about 1/10th of the lower 48 United States. Much of the deforestation is due to intentional burning to clear land for agriculture. In addition, the hotter and drier conditions brought by climate change are increasing the number of fires in a region that has not experienced them historically.

The Amazon sequesters an enormous amount of carbon—equivalent to 10 years worth of global emissions. Woods Hole Research Center studies the impact of these fires on the local and global climate, and helps government agencies anticipate at-risk areas, in order to more efficiently deploy firefighting resources. Follow @WoodsHoleResearchCenter to see more of their work.
August 22, 2019

The Case for Climate Rage

A lot of climate communication takes a dispassionate look at the problem. Amy Westervelt wrote an excellent piece arguing for the role of emotion and even anger in confronting & communicating climate change.

She also provides an excellent starter reading list:

The story of climate change, both its history and its future, needs to be told by people who have already experienced injustice and disempowerment, people who are justifiably angry at the way the system works. And some of those stories are beginning to be told.

I’d pair that with Maria Bustillos’ piece on the relation between collective and individual responsibility — Pascal’s Climate.

Understanding Climate Sensitivity: What’s up with the error bars?

The Earth’s climate sensitivity is the rise in our planet’s average temperature brought about by doubling carbon dioxide levels. Before the Industrial Revolution, CO₂ levels were at 280 parts per million. This year we hit 415 parts per million, so we’re almost halfway towards a CO₂ doubling compared to pre-industrial times.

Climate scientists estimate that the warming brought about by a CO₂ doubling — our climate sensitivity — lies between 1.5℃ and 4.5℃. Why does this prediction have such a wide range? How do climate scientists arrive at this number? If you’re interested in these questions, Zeke Hausfather at Carbon Brief has an excellent explainer from last year on how scientists estimate Earth’s climate sensitivity.


More Climate News

This is a remarkable statistic: “By the end of the summer, about 440 billion tons (400 billion metric tons) of ice — maybe more — will have melted or calved off Greenland’s giant ice sheet, scientists estimate. That’s enough water to flood Pennsylvania or the country of Greece about a foot (35 centimeters) deep.

Tree cover can cool down a city block by as much as 10 degrees Fahrenheit

Alie Ward interviews Dr. Samantha Montano about disasters, on the brilliant and funny Ologies podcast

As wildfires get worse, insurers pull back from riskiest areas

How firefighters in California are preparing for future fires

How can we do right by future generations?

A study found that more aggressive spiders were more likely to survive once a hurricane had passed

Fracking boom tied to methane spike in Earth’s atmosphere

Fracking may be a worse problem for climate change than we thought

Iceland mourns loss of a glacier by posting a warning about climate change

Ellen Swallow Richards: MIT’s first female student

Before Rachel Carson was born, Richards wrote and lectured that a direct link could be drawn between the well-being of humans and the safety and cleanliness of the environment in which they lived. At the turn of the 20th century, as if she was anticipating many of the discussions taking place today in the age of the Anthropocene, Richards said, “The quality of life depends on the ability of society to teach its members how to live in harmony with their environment, defined first as the family, then with the community, then with the world and its resources.”

“The world’s biggest ever climate mobilisation was led by children. It’s time adults stepped up.” Find a climate strike happening near you.

The broader importance of #FridaysForFuture

How one billionaire could keep three countries hooked on coal for decades

July was officially the hottest month ever recorded

As Greenland melts, its sand is becoming increasingly valuable

In order to understand the brutality of American capitalism, you have to start on the plantation. That’s the tile of sociologist Matthew Desmond’s piece in the remarkable 1619 project, a New York Times production exploring the history and enduring legacy of slavery in the United States. Read more stories from this project here, or check out the podcast. If you’re an educator, the Pulitzer center has published a school curriculum around this project.

Another excellent and deeply historically researched read on the links between slavery and American capitalism is the book This Half Has Never Been Told.

A history of estimating global CO2 emissions

How people in Phoenix, Arizona are adapting to warming temperatures

The US Government is moving to weaken the Endangered Species Act

The Washington Post has a new series about places that have already warmed by ~2 degrees Celsius, roughly double the global average. Here’s the first piece, on New Jersey & Rhode Island — the two lower 48 states with the highest level of warming so far.

The tweet above shows a screen capture of an FAQ from the Hurricane Research Division of NOAA responding to some of the more creative and outlandish ideas for combating hurricanes.

The Thin Orange Peel

Here’s an interesting fact I learnt this week. The atmosphere is thinner than you might think — and it’s uneven. The part of the atmosphere in which all weather occurs is called the troposphere. This layer contains 99% of water vapor, and makes up 75% of the atmosphere by mass. It turns out that at the poles, the troposphere ends at roughly the same height as Mt Everest, while at the equator, it extends to about twice this height.

The picture below shows us what this layer looks like in practice. The orange layer is the troposphere, the white layer is the stratosphere, and the blue layer is the mesosphere.

Image: NASA / Wikimedia (Public Domain)

Nearly everything we think of as the atmosphere — every cloud that we’ve ever seen — exists in that thin orange peel. If you scaled an orange up to the size of the Earth, it’s skin would be about 30 times thicker than Earth’s troposphere.

That’s all for this week, see you next time!

Clogging Earth's Heat Drain

The Rate of Change: August 12, 2019

A Brief Guide to Human-Sized Numbers

One of the things that makes climate science confusing is the huge numbers thrown around. Numbers like Gigatons, Terawatts, or Exajoules. It’s hard for numbers this large to feel real to us.

One way to tackle this problem is to divide a very large number by another large number, to end up with a human-sized number. This is like how the size of an economy is easier to understand when expressed per capita.

For example, the total energy that the Earth absorbs from the sun each day is an unrelatably massive number — 10 Zettajoules. (A Zettajoule is 10^21 Joules, or a thousand billion billion Joules. By comparison, annual human energy consumption is about half a Zettajoule.)

This is an unwieldy number. However, if we divide this by the surface area of the Earth, and by the number of seconds in a day, we find that on average, every square meter of the Earth receives about 240 Joules of solar energy per second (these numbers are all after taking into account that our planet reflects away 30% of sunlight).

The term ‘heat flux’ (or energy flux) tells you how much energy is received or emitted by one square meter of surface area in one second. The more intense the energy flow, the higher the heat flux.

So Earth’s incoming solar flux, averaged over the entire planet, is roughly 240 Joules / second / square meter, or 240 Watts / square meter (240 W/m², for short).

How does this number compare to everyday things? If I sat on the ground, I’d be warming the patch of Earth underneath me with a heat flux of about 50 W/m². If I placed my laptop on the ground while it was running, it would heat the Earth under it with an intensity of 100 W/m².

So measuring things this way puts climate-sized numbers and human-sized numbers in the same ballpark.

Worth remembering: The Earth receives energy at a rate of ~240 W/m² from the Sun. That’s our incoming solar flux.

(If you’ve taken some physics, you might have heard that the solar constant is ~ 1360 W/m². That’s the maximum solar flux at the equator, facing the sun, without any clouds. To take into account day and night, and the variation across Earth’s curved surface, we divide this number by 4. Also, Earth reflects away 30% of incoming light, so we multiply this number by 70% — the fraction of sunlight absorbed by the planet. All together, 1360 * 0.7 / 4 ≈ 240)

Where does the energy go?

As the Earth absorbs the sunlight raining down on it, its atoms and molecules start to jiggle. We call this collective jiggling temperature.

Quantum mechanics teaches us that when atoms and molecules jiggle, they emit photons. Each of these photons carries away a tiny bit of energy (a quantum of energy).

This is how stuff gets rid of excess energy. The hotter an object, the more heat it sheds in the form of photons. This is why when you look at things with an infrared camera, hotter objects glow more brightly than cold ones.

Image: Infrared Dog. NASA/IPAC

There’s a straightforward equation connecting the temperature of an object to its heat glow. Using this relationship, an infrared thermometer can tell you something’s temperature, just by looking at its invisible glow.

(Fun fact: if you point an infrared thermometer at the sky, the temperature it displays measures the greenhouse effect.)

Here’s that equation:

T represents the temperature, measured in Kelvin. The symbol σ is a conversion factor between temperature and heat flux, known as the Stefan-Boltzmann constant.

With this equation in hand, you can work out how much heat is radiated by an object at any temperature. Just plug in a temperature, and it’ll spit out a heat flux.

Let’s take a stab at using this equation to predict planetary temperatures. Spoiler alert: we’ll get it wrong, but we’ll learn something interesting.

Predicting Planetary Temperatures

Imagine that we created Earth from scratch, as a frozen, lifeless rock that’s as cold as the background temperature of outer space. We gently place this planet into Earth’s orbit. All of a sudden, sunlight starts streaming in. As a result of all this energy pouring in, Earth’s temperature rises.

Here’s an animation depicting this process (you might recognize this cartoon model from the previous newsletter.)

The yellow pile represents the energy coming in from the Sun, which pours in at a rate of 240 W/m². The red pile is the heat that we radiate (measured in the same units). The thermometer measures our temperature.

In the previous newsletter, we saw how any energy imbalance (energy in minus energy out) causes the temperature to change. Since the yellow pile exceeds the red, the planet warms up.

As the temperature rises, so does Earth’s heat glow. And so the red pile also starts to grow.

Eventually we reach a trade-off, where the two piles balance each other, and the temperature stabilizes. So this feedback mechanism automatically adjusts Earth’s temperature in response to the incoming energy, a bit like how a thermostat maintains a temperature.

The Kitchen Sink Analogy

This balancing process can be a little hard to think about. So here’s an analogy to help, that comes to us from the French physicist Joseph Fourier. In his classic 1827 paper that described for the first time how Earth maintains its temperature, Fourier writes that you can think about Earth’s heat flow as “analogous to [..] a vessel which receives, through its upper opening, a liquid [..], and which allows liquid to escape at a precisely equal rate through one or more openings.”

Fourier was imagining something like a bathtub or a kitchen sink, with water pouring in from a faucet above, and a drain from which water flows out.

Here’s an animation of this process, created by my amazing colleague Shefali Nayak.

In a leaky sink or bathtub with water pouring in, the water level finds a stable balance

At first, there’s more water flowing into the bathtub than flowing out. So, the water level rises. But as the water rises, the added weight of all this water pushes down more forcefully. So the outflow increases.

Eventually, the water level reaches a balance, where the flow coming in from the faucet exactly balances the flow going down the drain. (You can see this effect for yourself by punching a hole in a paper cup and placing it under a stream of water.)

What happens if you turn up the faucet?

Turning up the faucet raises the water level to a new stable balance.

If you turn up the faucet to increase the incoming water flow, the water level rises, until it reaches a new balance where the flow out once again matches the flow in.

It’s the same idea with Earth’s energy balance. The incoming solar energy is like the water pouring in, and the heat that we emit to space is like the water flowing down the drain. Our temperature is like the water level in this analogy. Just as the water level adjusts itself in response to the incoming flow, Earth’s temperature does the same thing in response to our incoming energy flow.

A Look at the Numbers

We can express this balance as a simple equation:

We know that Earth’s incoming energy flow is 240 W/m². The outgoing energy flow — the heat that we radiate into outer space — is determined by the T⁴ law that we encountered earlier.

So,

Solving for the temperature, we arrive at a planetary temperature of 255 Kelvin, or about -18C (0F).

(Notice that we didn’t mention how big the planet is. That’s because the planet’s size cancels out. A bigger planet will absorb more sunlight, but it will also radiate more heat. Both quantities grow in proportion to surface area. So, as long as we’re measuring heat flow per square meter of surface, we don’t need to worry about the planet’s size.)

That’s way too cold — about 33 C colder than Earth’s actual average temperature. The reason we were off by so much is that we didn’t account for the greenhouse effect. Without the warming influence of the atmosphere, Earth would be completely frozen over, like a giant snowball. (As it turns out, this calculation correctly tells us the temperature at the top of our atmosphere, above the region where the greenhouse effect acts.)

So this model is clearly wrong (or rather, it’s incomplete). But it’s still useful.

To see why, let’s think about the four planets closest to the Sun. Here’s the solar flux (the incoming energy flow) absorbed by the four innermost planets, after accounting for each planet’s albedo.

To get these numbers, I looked up the solar irradiance of each planet in NASA’s Planetary Fact Sheet. To convert that to the average solar flux absorbed by the planet, multiply by (1 - Bond albedo) and divide by 4.

Notice that Venus is an outlier. It’s closer to the Sun than we are, so you’d expect its solar flux to be higher than ours. The reason this value is so low is that Venus is mostly blanketed by clouds, and so 77% of the light that strikes Venus bounces off.

Now that we have the incoming energy flow for each planet, we can try to predict its temperature.

Here, try it yourself, by playing with this little interactive website.

So what do we find? The image below compares the predicted temperatures for each planet, based on our very simple heat radiation model, to the actual temperatures observed on these planets (which you can find here).

This is pretty interesting.

We get surprisingly close to the observed temperatures of Mercury and Mars. (The exact values will differ a bit based on what references you use, but the trend is clear.)

However, when it comes to Earth and Venus, we’re way off. For Venus, our prediction is spectacularly wrong!

You already know why this is — the greenhouse effect. Our model assumed no atmosphere or greenhouse gases. Turns out, this is a pretty good assumption for Mercury and Mars, so we more or less nailed those predictions. But when it comes to the Earth, and especially Venus, neglecting the warming effect of the atmosphere means that this simple model is way off in its predictions.

The last row of the image is the difference between the actual planetary temperature and our predicted temperature (also sometimes called the planetary equilibrium temperature, or the planet’s blackbody temperature). This temperature difference measures the strength of the greenhouse effect on each planet.

Adding in the Greenhouse Effect

Let’s do one last thing. We’ve seen how we can model Earth’s temperatures by ignoring the greenhouse effect. Doing this, we get the wrong temperature.

What if we fiddle with our simple model, and try to work out how much incoming energy it would take to heat the Earth up to our actual temperature?

I encourage you to try this out for yourself. Set the slider in this interactive to Earth’s solar flux. Then, slowly move the slider to the right, until the temperature hits 15° C, the average temperature on our planet. (If you overshoot you can always step back.)

If you do that, you’ll discover something like this:

The picture on the left is what things look like at the top of our atmosphere, where it’s cold, and we’re above the effect of the greenhouse gases.

The picture on the right is what things look like on Earth’s surface.

According to the picture on the right, Earth’s surface emits 390 W/m² of infrared heat.

According to the picture on the left, at the top of the atmosphere, only 240 W/m² of infrared heat makes it out to space.

Together these pictures teach us that out of the 390 W/m² of infrared heat that Earth’s surface emits, only 240 W/m², or about 60%, makes it all the way out to space. The remaining 150 W/m², or 40%, is absorbed by greenhouse gases and sent back down to us, adding to our yellow pile.

So this is how the greenhouse effect works. Part of the heat that we radiate is sent back down to us, similar to how those emergency reflective blankets keep people warm. The difference between the piles on the left and the right picture is 150 W/m² — this number is another way that scientists quantify the strength of our greenhouse effect.

Going back to the water analogy, this is somewhat analogous to when the drain in your bathtub is partially clogged with hair (ugh), and so the water level in your bathtub rises to a higher level.

If you clog the drain, the water level rises, until it settles into a new equilibrium.

Greenhouse gases are clogging Earth’s heat drain. Just as every hair that you shed in the bathtub adds to the cumulative clogging of your shower drain, and causes an incremental rise in water level, every unit of CO2 that we emit has a similar effect on Earth’s temperature.

Historically, our partially clogged heat drain wasn’t a bad thing. It kept our planet at a comfortable, habitable temperature, instead of being frozen over. But what we need to worry about today is the very sudden, massive surge in this clogging, from all the greenhouse gases we’ve added over the last century.

So the next time the you find yourself cleaning a clogged shower drain, you can think about how your situation is a metaphor for our planet’s fate.


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Last Week in Climate News

One of the biggest recent climate stories was the publication of the new UN special report issued on Climate Change and Land.

Robinson Meyer at the Atlantic did a spectacular job of covering this story, and driving home the magnitude of the stakes involved.

Christoper Flavelle covered the story in NYT.

Here’s Carolyn Kormann’s writeup in The New Yorker.

Rebecca Hersher and Allison Aubrey covered this story for NPR.

Carbon Brief has an in-depth summary of the report.

Here’s the executive director of Project Drawdown on how changing our land use and farming patterns can make a dent in addressing climate change.

The Trump administration announced plans to significantly weaken the Endangered Species Act, the US’s bedrock conservation law. By Lisa Friedman in NYT.

A Quarter of Humanity Faces Looming Water Crises. Somini Sengupta reports in NYT.

Alan Alda in conversation with climate scientist Katherine Hayhoe

How cheap does energy storage have to get before it can enable a 100% renewable energy system? By David Roberts in Vox.

What Worries Iceland? A World Without Ice. By Liz Alderman in NYT.

At least 60 people have been killed and over 200 thousand have been displaced by floods in the Indian state of Kerala. Muhammed Sabith reports in The Wire. This comes only a year after the previous monsoon’s extreme rainfall caused floods in Kerala.

Iceland is creating a memorial to a lost glacier.Okjökull—a once-iconic glacier that has melted away throughout the 20th century and was declared dead in 2014.

Excellent visualization of the inequalities in urban temperatures, mapped in five US cities. By Nadja Popovich and Christopher Flavelle in NYT.

“new research shows that temperatures on a scorching summer day can vary as much as 20 degrees across different parts of the same city, with poor or minority neighborhoods often bearing the brunt of that heat.”

Is eating seafood climate-friendly? It’s complicated. Informative video by Eve Andrews and Daniel Penner in Grist.

India plans to cut coal imports by a third. At the same time, it plans to increase domestic coal production, and is in talks to build coal mines in Australia.

Climate change made European heatwave up to 3°C hotter. By Quirin Schiermeier in Nature News.

Ulaanbaatar, Mongolia — the coldest capital city on Earth — also has one of the world’s worst cases of wintertime air pollution. Emily Kwong reports for NPR.

Hawaii’s snails are disappearing at a faster rate than any animal on Earth. A short documentary in The Atlantic. For more, read Ed Yong’s piece in the Atlantic, The Last of Its Kind.


That’s all for this week. See you next time!

"Dark Heat" and Earth's Energy Imbalance

The Rate of Change: July 23, 2019

To understand why global warming happens, we need to think about Earth’s energy balance.

Here’s a map of the incoming solar energy that Earth receives.

The blue stuff is the energy that reaches the surface, and the bright white spots are either clouds, snow, or ice, which reflect the Sun’s light and shade our planet.

If this was the end of the story, we’d keep getting hotter and hotter, with no limit (although I know it might feel like that these days). Somehow, we also need to get rid of all this energy.

The way we do this is by glowing with invisible light, through what the mathematician Joseph Fourier poetically called ‘dark heat’ (or rather, he called it chaleur obscure, because he was French).

Today, we use the rather less poetic term infrared radiation. Climate scientists sometimes refer to this as our ‘outgoing longwave radiation’. But don’t let the names confuse you. We absorb visible light and we emit dark heat.

If a thing gets hot enough, like lava, or the red-hot embers after a fire, then the heat becomes so intense it’s no longer dark. It leaks into the visible range. But on average, Earth’s relatively moderate temperature is safely inside the range of dark heat. (Interestingly, although this heat is dark to our eyes, it’s visible to heat-sensing snakes.)

Here’s what this dark heat looks like, as seen by satellite. This is Earth’s invisible glow.

Seen from this high view, clouds obscure Earth’s heat and show up as blue or white cold spots. That’s because, in addition to their role in providing shade, clouds can also act like a blanket, trapping our heat and keeping the Earth warm.

Clouds are complicated. When it comes to incoming solar energy, they cool us down with their shade. When it comes to our outgoing heat energy, they warm us up with their blanket-like behavior. (Or as a physicist might say, clouds are white in visible light but act as black bodies in the infrared spectrum).

Which of these wins out — cooling or warming — has to do with the specifics of the type of cloud. So to predict future climate, scientists have to model the nitty-gritty details of how clouds will form in the future. This is one of the big reasons why climate predictions are hard.

But let’s take a step back and talk about temperature.

For Earth’s temperature to be stable, the incoming energy from the Sun needs to exactly balance the outgoing dark heat. Any imbalance means that we’re either heating up or cooling down.

Here’s an oversimplified but instructive cartoon model. Let’s think of these yellow blocks as representing the energy that we get from the sun. The red blocks symbolize our dark heat. And the thermometer measures our temperature.

All these numbers represent global average quantities, so the numbers are averaged over the entire planet. In the picture above, the two energy piles are perfectly balanced and cancel each other out. So, our temperature remains stable.

Now, let’s say we add a block of energy to our incoming pile. This could happen through the greenhouse effect, or it could happen if the Sun grew considerably brighter (as ours is scheduled to do over billions of years). We then end up with a picture like this.

So now we’re absorbing more energy than we’re radiating. That’s going to raise the temperature.

But there’s a puzzle hidden here. If we’re gaining more energy than we lose, why don’t we keep getting hotter forever? What stops this energy imbalance from incinerating the planet?

The answer comes from basic physics. When you look at things with a thermal camera, you see that as a a thing’s temperature rises, it glows more brightly with invisible, dark heat. I mean, just take a look at how this Pomeranian emits heat!

Image: NASA/IPAC, modified by Wikipedia

In the nineteenth century, scientists worked out the exact relationship between an object’s temperature and its heat glow. (As a historical side note, explaining this law won Max Planck a Nobel Prize and led to the birth of quantum mechanics.)

You can see this bright glow in this NASA satellite image of the invisible heat energy radiated by the Earth during the 2003 European heatwave.

https://atrain.nasa.gov/images/multimedia/AquaCERESHeatwave_hr.png

So as our temperature rises, our dark heat emissions rise with it. And so the red pile also starts to grow, until it balances the yellow pile. Once this happens, the Earth’s temperature stabilizes at its new, hotter level.

(Why does the temperature stabilize? If the red pile overshoots the yellow, we’ll start losing more heat than we gain, which will cool us down, lowering the temperature and therefore also the red pile. So this is a self-stabilizing mechanism.)

It all comes down to simple physics: if we gain more energy than we lose, we warm up.

This process also works in reverse. Imagine if our Sun were to somehow get dimmer. This can happen in the aftermath of a massive volcanic eruption, like the Mount Pinatubo eruption in 1991, which caused global temperatures to drop by nearly half a degree Celsius in a single year. Some of the more extreme geoengineering proposals seek to emulate this idea by releasing particles into the atmosphere to dim the Sun.

In our cartoon picture, this will take away a block of incoming solar energy.

So now we’re losing more energy than we gain from the Sun. You know what comes next. We get colder.

And as Earth’s temperature drops, our dark heat glows dimmer. That red bar starts to shrink until eventually, we end up back in a balance, and the temperature stabilizes into a lower level.

So, to understand where Earth’s temperature is going, we need to understand our planetary energy balance.

If there’s a positive imbalance (energy in minus energy out), we’ll warm up, until we reach a new, hotter balance. If the imbalance is negative, we’ll cool down. And if it’s zero, then Earth’s global thermometer won’t budge.

So, what is our energy imbalance? It turns out that we understand this very well. Climate scientists refer to this energy imbalance — the difference between the yellow and the red piles — as Earth’s radiative forcing.

Let’s talk numbers.

Our incoming solar energy averaged over the Earth’s surface is about 240 W/m², or 240 Watts / square meter. (Working out this number starting from the temperature of the Sun turns out to be a fun physics exercise.. I can feel you judging me right now).

If this were the only source of incoming energy, our planet would be way too cold. You can calculate that without any greenhouse effect, Earth’s average temperature would be -18 degrees Celsius, or about zero Fahrenheit! (This numerical coincidence is also the only redeeming feature of the Fahrenheit scale.)

So without any greenhouse effect, Earth would be a frozen rock. The greenhouse effect at pre-industrial levels effectively increased our incoming energy and warmed us up. You can think of this like adding to the yellow blocks in the picture above, which raised the Earth’s temperature, until the red blocks grew to catch up, and we settled into a warmer temperature balance.

That was 1750. Where are we today? Here’s a chart from page 14 of the 2013 IPCC report on the science of climate change. (Click to enlarge)

This figure tells us Earth’s energy imbalance in 2011 (or as climate scientists call it, Earth’s radiative forcing), as compared to 1750. It also tells us the contributions from different greenhouse gases. Unsurprisingly, the biggest contributor is carbon dioxide.

After adding up all the pieces, the report finds that Earth’s energy imbalance due to human causes is roughly 2.3 W/m². This is how much we’ve added to the yellow blocks since 1750.

What does this number mean? One way to think about it is to remember that we receive 240 W/m² from the Sun, and 2.3 is nearly a percent of 240. In other words, human-caused changes have increased our incoming energy by an amount roughly equivalent to the Sun getting brighter by one percent.

To be clear: I’m not saying the Sun became one percent brighter — I’m saying that between 1750 and 2011, the amount by which we’ve heated the Earth is as if we instead made the Sun a percent brighter.

For comparison, how much did the Sun’s brightness actually vary in that time period? The chart above tells us that this number is 0.05 W/m². Comparing this to 240 W/m², we find that this is a 0.02% variation in the Sun’s brightness — nearly 50 times smaller than the human-caused component.

This is how we know that global warming is human-caused.

So, today, we’re out of balance. We know that the yellow blocks exceed the red. And basic physics tells us that when there’s more energy going in to a box than there is leaving it, the box will warm up.

What’s more, the imbalance is growing. In 2011, it was about 2.3 W/m². The IPCC considers four different scenarios for how this number will grow by 2100. These Representative Concentration Pathways go by the names RCP2.6, RCP4.5, RCP6, and RCP8.5 (we encountered these pathways in an earlier newsletter). The numbers following RCP aren’t temperature changes, but are instead the energy imbalance in 2100, compared to pre-industrial levels.

So in 2100, we’re looking at an increasingly unlikely best case energy imbalance of 2.6 W/m², and a nightmarish worst case of 8.5 W/m². To get a better sense of what these numbers mean, just compare them to our incoming solar energy, which is 240 W/m². An energy imbalance of about 8.5 W/m² in 2100 would have an equivalent effect on temperature as the Sun becoming ~3.5% brighter than it was in 1750.

How much will we warm up?

We know that Earth’s energy has a positive imbalance — there’s more energy coming in than leaving. We know this will lead to an increase in Earth’s temperature. None of this is in any scientific dispute, as it relies on fundamental, well-understood principles of physics and chemistry. The mathematician and physicist Joseph Fourier first described this mechanism way back in 1827, and the theoretical and experimental details were well understood in the latter half of the 1800s.

Here’s the hard question. Exactly how much will our temperature increase?

The relationship between energy imbalance and temperature increase is known as Earth’s climate sensitivity. The climate sensitivity tells us how much Earth’s average temperature will increases when our energy imbalance increases by 1 W/m². In our cartoon picture above, it tells us how the thermometer responds to adding a yellow block. A high climate sensitivity means that a small energy imbalance will result in a large change in temperature.

In coming newsletters, we’ll dig into how we know what this number is, why predicting it is so hard, and we’ll add some more complexity to our simple cartoon picture of the Earth.


This Week in Climate News

French senators have approved a bill setting France on a new target to reduce greenhouse gas emissions and go carbon-neutral by 2050. (via @Sustainable2050)

Amid Heat Wave in New York, 50,000 Lose Electricity

How extreme weather leads to contamination that causes people to fall sick

I was using this real-time electricity map to track the carbon intensity of energy in New York, where I live. During the heat wave, the intensity peaked at well over 300 gCO2/kWh, whereas today is cooler and we are down to about 250 gCO2/kWh (which is still twice the annual average). As the map shows, the reason for this shift is the amount of natural gas we’re consuming, which ramps up during a surge in demand.

Why climate change is a human rights issue

In a report presented to the Human Rights Council on Friday, U.N. special rapporteur Philip Alston writes that climate change is an “unconscionable assault on the poor.”

Via @YaleClimateComm

In 2018, the carbon dioxide emissions of the US’s energy sector grew by 2.7%. According to the US Energy Information Administration, this is expected to dip down in 2019. The reason for this is falling coal use, which is being replaced by natural gas. Via @Peters_Glen

As the country ages and air pollution rises, chronic obstructive pulmonary disease is likely to be increasingly common in India

An incurable and progressive disease, chronic obstructive pulmonary disease moved up from the eighth spot to become second on the list of leading ways to die in India, over 26 years to 2016 – the year for which the latest data are available. Chronic obstructive pulmonary disease claimed more victims than either road accidents or suicides in 2016. It claimed more lives than diabetes, malaria, tuberculosis and breast cancer combined in 2016.

Via @airqualityindia

Heat Waves in the Age of Climate Change: Longer, More Frequent and More Dangerous

If you missed this interactive from last year, it’s worth checking out. How much hotter is your hometown than when you were born?

In the Indian state of Assam, nearly 4.3 million people have been displaced by floods and more than 100 people have been killed. Via @AmbaAzaad

France’s record-breaking heatwave made ‘at least five times’ more likely by climate change

Earth just had its hottest June on record, on track for warmest July (via @DrJoeHanson)

Flooding Kills Dozens in Nepal as Waters Rise Across Asia

Why Brazil's deforestation of the Amazon is a matter of international responsibility

Deforestation of the Amazon rainforest in Brazil is at its highest rate in a decade, according to new satellite data. This comes after president Jair Bolsonaro has loosened environmental regulations, cut enforcement budgets, and supported further development in the region.

Trees absorb carbon dioxide naturally, and are one of best tools we have to help stave off climate catastrophe – and the Amazon itself is a crucial carbon sink. This means responding to deforestation in Brazil has become a matter of international responsibility.

In 1856, Eunice Foote became the first person to discover that carbon dioxide is a greenhouse gas

Why history forgot the woman who discovered global warming

The female scientist who identified the greenhouse-gas effect never got the credit

Pretty much every reference I’ve read credited John Tyndall for the discovery that carbon dioxide is a greenhouse gas. However, Eunice Foote’s work on carbon dioxide preceded John Tyndall’s work by three years and identifies it as a greenhouse gas. Tyndall did not cite her work, although it’s unclear if he was aware of it. However, he was one of the five editors of the journal in which she published her work, and he published an unrelated article in the same edition of the journal in which she published. So it’s a bit surprising (to put it mildly) that he would be entirely unaware of her work.

That’s all for this week, see you next week!

The Rate of Change: July 15, 2019

Millennia from now, if there’s one piece of data that humans alive today will be known for, I think it would be this.

Carbon Dioxide Levels over the Past 10,000 Years

Image modified from the Keeling Curve

This graph shows us the historical record of carbon dioxide levels in Earth’s air, over the last 10,000 years. For most of this time, carbon dioxide levels were quite stable — that’s the relatively flat portion of the graph. Agriculture, cities and civilizations all got their start somewhere along those gentle slopes. This stability coincided with the moderate climate following the last ice age, which ended around 15 thousand years ago.

All the way on the top right, that dramatic spike is where we find ourselves today. The last time that carbon dioxide levels were as high as they are today was about 3 million years ago. Back then, global temperatures were 3 degrees Celsius warmer, and sea levels were about 20 meters (66 feet) higher.

(This classic XKCD comic explainer provides an excellent timeline of Earth’s temperature from the last ice age to the present day. By taking this long view, we can understand how unprecedented our current moment is.)

You might think that the carbon crisis is a historical problem, because we’ve been burning fossil fuels for hundreds of years. But take a look at this.

Carbon Dioxide Levels over the Past 10,000 Years: a Personal, Human-Centered View

Image modified from the Keeling Curve

Here’s an astonishing fact: humans have pumped more carbon dioxide into the air in my lifetime than in the time between my birth and the start of the Industrial Revolution.

If you look at all carbon dioxide added to the atmosphere since the Industrial Revolution, more than half was added after 1990. A quarter was added after 2007. Just 30 years — a single generation — accounts for half of all carbon emissions in the history of burning fossil fuels.

Here, look up your age in this chart created by Neil Kaye, a climate data scientist at the UK’s Met Office. It’ll tell you how big a slice of global fossil fuel emissions have occurred in your lifetime.

Image source: Neil Kaye, World Energy Data

So this is very much a modern problem.

Let’s zoom in closer to modern times. Here’s all of human industrialization in a graph.

Carbon Dioxide Levels From The Industrial Revolution to Present Day

https://scripps.ucsd.edu/programs/keelingcurve/wp-content/plugins/sio-bluemoon/graphs/co2_800k_zoom.png
Image: the Keeling Curve

Around 1750 marks the start of the Industrial Revolution, when humans figured out how to power machines by burning fossil fuels. From then on, our story has been one of accelerating greenhouse gas emissions.

The units of measurement in these graph are parts per million of our atmosphere. As I write this, we’re at about 414 parts per million of carbon dioxide — 0.0414% of the air that we breathe is CO2. The green line marks when we crossed 400 ppm.

Before 1958, the data comes from analyzing air trapped in frozen bubbles deep beneath the surface of Antarctica’s ice (the deeper you drill, the older the ice). From 1958 onwards, the data comes from the Keeling Curve, a detailed record of carbon dioxide levels based on direct measurements at an observatory in Hawaii. The Keeling Curve is one of the most important vital signs tracking the trajectory of our climate, and it looks like this:

The Keeling Curve (as of July 1)

https://scripps.ucsd.edu/programs/keelingcurve/wp-content/plugins/sio-bluemoon/graphs/mlo_full_record.png
Image: the Keeling Curve

The curve has wiggles in it, corresponding to the annual seasonal cycle. But the overall trend is unmistakably clear. Every year, CO2 levels are rising.

When we eventually wean away from fossil fuels, this curve will start to flatten out. (It won’t move downwards immediately after our emissions stop — carbon dioxide stays in the air even after we stop adding more of it, because it takes a while for carbon to be reabsorbed by the Earth.)

How high this curve reaches will determine Earth’s eventual temperature. So it’s safe to say that this is one of the most consequential turning points in human history.

Footnote: By the way, the ice core data keeps going further and further back. If you look at the last 800 thousand years, carbon dioxide levels fluctuated rapidly, and so did the climate. Every rise and plummet in that graph is associated with a corresponding rise and plummet of global temperatures (it’s possible to infer temperatures of the deep past by analyzing the concentrations of various isotopes). From this long view, all of human civilization is confined to a narrow plateau of climate stability.

The Takeaway

You should know two things about the Keeling Curve, which measures carbon dioxide concentrations in our atmosphere.

First, CO₂ levels are strongly linked to Earth’s temperature.

The climate sensitivity measures how much Earth’s temperature will rise if carbon dioxide levels double. This number is very difficult to calculate because it involves complex feedback loops — as the Earth gets warmer, things like the cloud cover and the ice cover change, which in turn increase the rate at which the Earth is being warmed.

At the moment, climate scientists are confident that doubling CO₂ levels will likely result in a temperature rise of 1.5 to 4.5 degrees Celsius. (This is the temperature rise when the climate settles down into a new balance, which might be centuries after the doubling occurs. The short-term rise in temperature from a CO₂ doubling is likely between 1.5 and 2.5° C.)

The second thing to know about the Keeling Curve is that its slope is rising. With every decade, we’re emitting increasing levels of carbon dioxide. In other words, we’re accelerating our carbon emissions, at a time when we need to hit the brakes.

Three Compelling Ways To Think About the Keeling Curve

Neil Kaye broke down our fossil fuel emissions from 1751 onwards into 4 periods of equal emissions.

Here’s another way to look at this acceleration, by Kees van der Leun:

Finally, Gregor Aisch had the clever idea of wrapping the Keeling Curve around every decade, so you can see how our rate of emissions is changing. (Here’s an interactive version where you can find out the levels when you were born).

In the 1960s, carbon dioxide levels rose at a rate of less than 1 ppm/year. In this decade (2010 onwards), the rise was nearly 3 ppm/year. (As a reference, a rise of 1 part per million corresponds to adding 7.8 billion tons of carbon dioxide to the atmosphere.)

This acceleration of emissions makes climate change a modern problem.


Numbers to Know

A part per million, or ppm, is a standard measure of greenhouse gas concentrations. To convert from ppm to percentage, divide by a million and multiply by 100. So 400 ppm = 400 × 100 / 1,000,000 percent = 0.04 percent.

1 ppm of CO₂ corresponds to 7.81 billion tons of carbon dioxide, which is what you’d get from completely burning 2.13 billion tons of carbon. These three units are often used interchangeably.

1 ppm of CO₂ = 2.13 billion tons of Carbon = 7.81 billion tons of Carbon Dioxide

A billion tons of Carbon can be abbreviated as GtC, and a billion tons of Carbon Dioxide is abbreviated as GtCO₂. A common mistake (I’ve done this a few times) is to confuse GtC and GtCO₂. To go from a weight of carbon to a weight of carbon dioxide, you multiply by 44/12 = 3.67


How to talk to your kids about climate change

Climate scientist Katherine Hayhoe shared how she talks about climate change to children, in this piece by Megan Ogilvie on what we can do about climate change.

“By digging up and burning coal and gas and oil we are wrapping an extra blanket around the planet. And just like we overheat when someone puts an extra blanket on top of us, one that we didn’t need, the planet is overheating and it’s running a fever.”

One in every eight deaths is due to air pollution. Here’s what one person is doing about it.

Excellent interview with Christa Hasenkopf, the co-founder and CEO of the nonprofit OpenAQ, which makes real-time and historical air quality data freely available and easy to access. By Shannon Farley in Forbes.

Oceans are absorbing almost all of the globe’s excess heat

It’s not everyday that you see the word ‘zettajoules’ in a New York Times article. Tim Wallace reports. (via Dr. Ayana E. Johnson)

“Since 1955, more than 90 percent of the excess heat retained by the Earth as a result of increased greenhouse gases has been absorbed by the oceans, leaving ocean scientists like Eric Leuliette at the National Oceanic and Atmospheric Administration feeling that 90 percent of the climate change story is being ignored.”

The climate crisis in a tweet

The data comes from this source.

Here’s a depressing statistic from the same source.

“A measure of decarbonisation is the carbon intensity of total primary energy supply, which is a measure of the quantity of carbon dioxide emitted for every [unit] of energy supplied. Chart 9 shows there hasn’t been any significant decarbonisation of the world’s energy supply. The curve is almost flat.”

Here’s that curve for you.

The World’s energy hasn’t gotten cleaner since 1990

Yup, pretty flat alright.

As a whole, our global energy supply hasn’t gotten cleaner since 1990. However, our energy use has increased, and so our emissions follow along.

Calling plantations ‘forest restoration’ is putting climate targets at risk

By Simon Lewis and Charlotte Wheeler, in The Conversation.

“Of all the negative emissions technologies available, allowing natural forests to return is safe, often not costly, and brings many other obvious benefits. But forest restoration can only play the critical role that it needs to if it means the same thing to policy makers as it does to everyone else: restoring areas back to largely intact largely natural forest. A new definition of “forest restoration” that excludes monoculture plantations is needed.”

Los Angeles struck a deal on the largest and cheapest solar + battery-storage project in the world

Jeff McMahon report in Forbes. (Via Akshat Rathi)

To understand climate change, we need to understand Greenland

This new book looks worth a read.

Rising seas imperil the cables and power stations that power the internet

By Alejandra Borunda in National Geographic. This was an interesting thread about this issue.

What you can do about climate change

An excellent twitter thread by Rosemary Mosco.

On the emotional toll of climate work

David Corn wrote the recent Mother Jones cover story on the distinct burden of being a climate scientist. (Via Dr. Katherine Wiklinson)

The psychological toll of working as a climate scientist

On The Media’s Brooke Gladstone interviews David Corn, author of the piece above, and speaks with Priya Shukla, Ph.D. candidate at UC Davis.

On Air Pollution in America

Nadja Popovich reports in the New York Times.

Fact checking Trump’s claims on Air Pollution

By Robinson Meyer in the Atlantic.

One climate crisis disaster happening every week, UN warns

“Climate crisis disasters are happening at the rate of one a week, though most draw little international attention and work is urgently needed to prepare developing countries for the profound impacts, the UN has warned.”

Fiona Harvey reports in the Guardian. Via Carl Zimmer.

Ancient life awakens in thawing permafrost

Thankfully, it’s just 1,500 year old mosses. For now. By Diane Ackerman in the Washington Post. Via Deborah Blum.

On the role of alarm in climate communication

By Marc Tracy in the New York Times.

Storks are making a comeback in Britain

By Isabella Tree in the Guardian.

Why you should talk about climate change

Excellent piece by Julia Rosen in LA Times.

What Delhi’s future holds

By Nilanjana Roy in the New York Review of Books. (Via Hari Kunzru)

The melting of Antarctica’s glaciers is accelerating

By Adam Morton in the Guardian.

24 governors call on Trump to halt rollback on rules for clean cars

By Hiroko Tabuchi in the New York Times.

What can I do about climate change? Resources for school workshops

This looks like a great resource, by Rebecca Willis.

Alaska’s Historic Heat Wave

Parts of Alaska experienced temperatures in the 30s Celsius (or 90s F), breaking all time records.

Historic Heat in Alaska
Image: NASA Earth Observatory

UK emissions cuts must accelerate to meet its target of net-zero emissions by 2050

Although the UK has been reducing its emissions, it is currently falling short of its legally binding target. Simon Evans reports for Carbon Brief. Akshat Rathi also covered this story at Quartz.

Young Activists Are Planning National Protests To Push Democrats On The Climate Crisis

By Zahra Hirji in Buzzfeed News.

Plastic has a big carbon footprint, but so do many of its alternatives

Christopher Joyce reports for NPR’s All Things Considered.

In maps: How Chennai grew over its lakes

By Teja Malladi &  Kaavya Kumar in Scroll.in

Life in a City Without Water: Anxious, Exhausting and Sweaty

By Somini Sengupta in the New York Times.


It’s not just you.

That’s all for this week. See you next week!


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