Nostr notes by Zeke Hausfather

March 2026 was the 4th warmest March on record for the ...

2026-04-02T15:10:59Z

March 2026 was the 4th warmest March on record for the planet's surface in the ERA5 dataset, coming in at 1.48C above preindustrial levels.

The new 2025 Global Carbon Budget finds that fossil fuel ...

2025-11-13T03:29:07Z

The new 2025 Global Carbon Budget finds that fossil fuel emissions will reach a new high in 2025. Total CO2 emissions (including land use) remain flat at 2024 levels.

While the land sink is up from 2024, carbon sinks are weakening: https://www.carbonbrief.org/analysis-fossil-fuel-co2-emissions-to-set-new-record-in-2025-as-land-sink-recovers/

In a UN speech today, President Trump said that "all of these ...

2025-09-23T17:02:14Z

In a UN speech today, President Trump said that "all of these [climate] predictions were wrong".

Back in 2019 I led a research effort to digitize old climate model projections and assess how well they did. Turns out they got future warming pretty spot on!

With only four months of the year still to report, I estimate ...

2025-09-07T15:01:32Z

In reply to nevent1q…28h5
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With only four months of the year still to report, I estimate that 2025 will be either the second (~33% chance) or third (~66% chance) warmest year on record. There is effectively zero chance that it will set a new record or be lower than the third warmest at this point.

August 2025 was the third warmest August on record after 2023 and ...

2025-09-07T15:01:26Z

August 2025 was the third warmest August on record after 2023 and 2024 at approximately 1.3C above preindustrial levels.

This continues a string of recent months a bit cooler than the exceptional 2023/2024 temperatures but warmer than any prior years.

Proud to be part of an effort by 85 scientists from around the ...

2025-09-02T17:29:07Z

Proud to be part of an effort by 85 scientists from around the world to respond to a misleading DOE climate science report last month.

The fact that our rebuttal is more than 3x the length of the DOE report is a good example of Brandolini's Law in action... https://sites.google.com/tamu.edu/doeresponse/home

Its only the high end warming outcomes of >4C that have become ...

2025-07-29T21:04:42Z

In reply to nevent1q…5a5m
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Its only the high end warming outcomes of >4C that have become increasingly unlikely as the world has moved toward lower emissions scenarios. The wide range of climate sensitivity and carbon cycle feedbacks still makes it impossible to rule out up to 4C: https://journals.sagepub.com/doi/10.1177/29768659241304854

Specifically, in our paper we argue that RCP4.5 or RCP6.0 are ...

2025-07-29T21:04:35Z

In reply to nevent1q…a76u
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Specifically, in our paper we argue that RCP4.5 or RCP6.0 are more realistic representations of 2100 warming under current policy than the increasingly implausible RCP8.5 scenario. But the lower of those two – RCP4.5 – gives a 2100 warming range of 1.8C to 4C!

The EPA cited my paper in their argument against the endangerment ...

2025-07-29T21:04:30Z

The EPA cited my paper in their argument against the endangerment finding today. However, their point is completely backwards: my paper actually supports the EPA's 2009 range of 1.8C to 4C warming by 2100. https://www.nature.com/articles/d41586-020-00177-3

"If you don’t worry about it now, it’s too late later on. ...

2025-07-11T16:27:06Z

In reply to nevent1q…ymvh
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"If you don’t worry about it now, it’s too late later on. [..]We are passing down extremely grave problems for our children, when the time to solve the problems is now"

Check out Sagan's 1985 congressional testimony on climate change here: https://www.youtube.com/watch?v=Wp-WiNXH6hI

Sagan really got the fundimental challenge of longer-term ...

2025-07-11T16:27:00Z

In reply to nevent1q…u9zn
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Sagan really got the fundimental challenge of longer-term problems like climate:

"Because the effects occupy more than a human generation, there is a tendency to say that they are not our problem — of course, then they are nobody’s problem..."

"The power of human beings to control and change the ...

2025-07-11T16:26:55Z

"The power of human beings to control and change the environment is growing as our technology grows. At present, we clearly have reached the stage where we are capable to make significant changes in the global climate."

-Carl Sagan, 1985

This comparsion in the NYTimes today is pretty stark. China is ...

2025-06-30T22:45:35Z

This comparsion in the NYTimes today is pretty stark. China is racing ahead to be a high-tech exporter of 21st century technologies, while the US is doubling down on being a petro-state exporting the technologies of the 19th century: https://www.nytimes.com/interactive/2025/06/30/climate/china-clean-energy-power.html

Is global warming accelerating? Over at The Climate Brink I argue ...

2025-06-30T17:06:37Z

Is global warming accelerating? Over at The Climate Brink I argue that the consilience of evidence from surface temperatures, climate models, forcing changes, ocean heat content, and earth energy imbalance all point toward yes: https://www.theclimatebrink.com/p/the-great-acceleration-debate

To put it another way, it takes the approach of actively ...

2025-06-28T15:23:52Z

In reply to nevent1q…ejdx
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To put it another way, it takes the approach of actively penalizing the technologies of the 21st century and subsidizing the technologies of the 19th century. As solar, batteries, and electrification are rapidly adopted by the rest of the world, we are stepping backwards.

The latest version of the Senate's BBB is a death sentence ...

2025-06-28T15:23:46Z

The latest version of the Senate's BBB is a death sentence for US energy leadership and a giant gift to China.

It eliminates tax cuts for solar that have been around since 2005, adds a new tax on solar after 2027, and creates a new direct subsidy for coal.

These 70% declines in Chinese SO2 emissions have occurred as the ...

2025-06-10T15:55:49Z

In reply to nevent1q…xdwy
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These 70% declines in Chinese SO2 emissions have occurred as the national government has brought in a series of air-pollution measures. These declines have added around 0.06C to global warming since 2006, or approximately 12% of the around 0.5C warming the world experienced between 2007 and 2024.

Clean air rules are driving a rapid decline in sulphur emissions ...

2025-06-10T15:55:43Z

In reply to nevent1q…ywsp
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Clean air rules are driving a rapid decline in sulphur emissions around the world. Global sulphur dioxide (SO2) emissions have fallen by around 40% since the mid‑2000s. Chinese SO2 emissions have fallen by more than 70% during that period.

There is around half a degree of warming today that is ...

2025-06-10T15:55:37Z

In reply to nevent1q…pkmn
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There is around half a degree of warming today that is “hidden” by aerosols. Without the cooling from sulphate and other aerosols, today’s global temperature would already be close to 2C above pre‑industrial levels, rather than the approximately 1.4C the world is currently experiencing.

Aerosols also have a substantial impact on human health, with ...

2025-06-10T15:55:31Z

In reply to nevent1q…ctcq
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Aerosols also have a substantial impact on human health, with poor outdoor air quality from particulate matter contributing to millions of premature deaths. Efforts to improve air quality around the world in recent decades have reduced aerosol emissions, bringing widespread benefits for health.

Human-caused emissions of aerosols – tiny, light‑scattering ...

2025-06-10T15:55:25Z

In reply to nevent1q…zf3c
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Human-caused emissions of aerosols – tiny, light‑scattering particles produced mainly by burning fossil fuels – have long acted as an invisible brake on global warming. This is largely because they absorb or reflect incoming sunlight and influence the formation and brightness of clouds.

I just published an explainer on aerosols and their role in the ...

2025-06-10T15:55:20Z

I just published an explainer on aerosols and their role in the climate that I've been working on for the past few months! It includes both how aerosols work, how emissions have changed, and how thats driven recent warming: https://www.carbonbrief.org/explainer-how-human-caused-aerosols-are-masking-global-warming/

Join us at 11 AM Eastern (8 AM Pacific) for a live Q&A and ...

2025-05-12T16:49:45Z

Join us at 11 AM Eastern (8 AM Pacific) for a live Q&A and the release of the Berkeley Earth April 2025 global temperature report: https://us02web.zoom.us/webinar/register/WN_k47CNFd5Q4aw6xJ13ptHFg#/registration

Large volcanic eruptions have a major climate cooling effect. But ...

2025-05-09T16:25:59Z

Large volcanic eruptions have a major climate cooling effect. But the eruptions we've had in the past 170 years have been relatively mild compared to those in the more distant past.

Here are climate model simulations of major eruptions since 1750 using FaIR:

it is.

2025-04-10T23:09:16Z

In reply to nevent1q…y5yg
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it is.

Here is how daily global temperatures have changed since the ...

2025-04-10T17:41:22Z

Here is how daily global temperatures have changed since the preindustrial (1850-1900) period in the Copernicus/ECMWF ERA5 dataset, with data through two days ago (April 8th):

Whenever I post about climate, skeptical folks inevitable respond ...

2025-03-24T19:26:01Z

Whenever I post about climate, skeptical folks inevitable respond with this graph. So I decided to do something radical: actually read the underling scientific paper and ask the authors.

As it turns out, it actually says the opposite of what skeptics claim: https://www.theclimatebrink.com/p/climate-skeptics-have-new-favorite

This record was unusual because it occurred during La Niña ...

2025-02-11T17:49:41Z

In reply to nevent1q…aape
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This record was unusual because it occurred during La Niña conditions, which have historically resulted in lower global January temperatures. January 2025 really stands out as anomalous compared to other La Niña years:

We've released the Berkeley Earth temperature update for ...

2025-02-11T17:49:36Z

We've released the Berkeley Earth temperature update for January 2025: https://berkeleyearth.org/january-2025-temperature-update/

It was the warmest January on record at 1.64C above preindustrial levels, and 0.09°C above the prior record set in 2024.

It is both the case that the 2% of the planet that is it United ...

2025-01-21T06:34:22Z

It is both the case that the 2% of the planet that is it United States is remarkably frigid at the moment, and that the world as a whole is at record-warm levels for this day of the year:

Scientists developed the first climate models in the late 1960s ...

2025-01-12T19:31:46Z

Scientists developed the first climate models in the late 1960s (for which the Nobel Prize in physics was recently awarded!).

How have these models held up against what happened in the real world after they were published? Surprisingly well, it turns out:

Great (and scary) visualization of 2024 daily temperatures ...

2025-01-10T18:30:35Z

Great (and scary) visualization of 2024 daily temperatures compared to prior years by the BBC today. Evocative of the iconic Joy Division album cover from 1979: https://www.bbc.com/news/articles/cd7575x8yq5o

A new perspective in Nature Climate Change argues that the ...

2024-12-04T18:48:03Z

A new perspective in Nature Climate Change argues that the discourse around climate tipping points risks "oversimplifying the diverse dynamics of complex natural and human systems and for conveying urgency without fostering a meaningful basis for climate action." https://www.nature.com/articles/s41558-024-02196-8

With ten months of the year now in, 2024 will be the warmest year ...

2024-12-02T23:35:42Z

In reply to nevent1q…te6f
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With ten months of the year now in, 2024 will be the warmest year on record in the ERA5 dataset, at around 1.59C (with a 95% confidence interval of 1.57C to 1.61C given uncertainty in December temperatures).

November 2024 was the second warming November on record in the ...

2024-12-02T23:35:36Z

November 2024 was the second warming November on record in the Copernicus ERA5 dataset, at 1.62C above preindustrial levels. It was second only to November 2023, which was 1.75C above preindustrial.

Has global warming accelerated in recent decades? If we look at ...

2024-12-01T16:44:19Z

Has global warming accelerated in recent decades? If we look at the rate of warming between 1970 and 2008 and extend it through present, we see that almost all years since 2015 are above the previous trend.

So what is the takeaway here? The weirdest aspect of the ...

2024-11-25T17:25:03Z

In reply to nevent1q…d8lh
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So what is the takeaway here? The weirdest aspect of the 2023/2024 El Niño event remains its early rise in global temperatures, occurring months before the peak of El Niño conditions. The persistence of high temperatures has been unusual, but the coming months will tell us just how unusual it is.

However, if we include more moderate El Nino events, there is one ...

2024-11-25T17:24:56Z

In reply to nevent1q…67pt
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However, if we include more moderate El Nino events, there is one in 1958 that saw a spike in global temperatures 12 months after the event peaked that is not too far off from what we are seeing today:

In a new post over at The Climate Brink I take an in-depth look ...

2024-11-25T17:24:50Z

In a new post over at The Climate Brink I take an in-depth look at how "weird" the recent El Nino event was. Compared to prior strong events, global surface temperatures rose earlier and high temperatures have persisted for longer: https://www.theclimatebrink.com/p/how-unusual-is-current-post-el-nino

Gavin Schmidt (@ClimateOfGavin) and I have a guest essay in ...

2024-11-13T17:41:45Z

Gavin Schmidt (@ClimateOfGavin) and I have a guest essay in today's New York Times about the exceptional and not fully explained recent global temperatures, and climate science can become more "operational" to address these questions: https://www.nytimes.com/2024/11/13/opinion/climate-change-heat-planet.html

yes, as far as we can tell: ...

2024-11-12T19:18:10Z

In reply to nevent1q…nmgg
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yes, as far as we can tell: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021RG000757

As Glen notes, "The world has failed at 1.5°C, but this does ...

2024-11-12T17:59:23Z

In reply to nevent1q…q7sq
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As Glen notes, "The world has failed at 1.5°C, but this does not mean the world has failed. While crossing 1.5°C is a disappointing milestone, it does give the opportunity to reframe the problem. Staying aligned with the Paris Agreement ‘well below 2°C’ ambition is still very possible."

Is limiting the temperature increase to 1.5°C still possible? ...

2024-11-12T17:59:17Z

Is limiting the temperature increase to 1.5°C still possible? Yes, but only in a model.

Some new commentary by Glen Peters (@Peters_Glen) provides a fitting swan-song for our now-unachievable ambition: https://journals.sagepub.com/doi/10.1177/29768659241293218

For more details, see my write-up of the new paper over at The ...

2024-11-11T15:02:57Z

In reply to nevent1q…ah9v
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For more details, see my write-up of the new paper over at The Climate Brink: https://www.theclimatebrink.com/p/durability-of-carbon-dioxide-removal

But the science is clear: if we want to stabilize global ...

2024-11-11T15:02:52Z

In reply to nevent1q…45qa
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But the science is clear: if we want to stabilize global temperatures, only permanent removals (>1,000 years) can credibly neutralize ongoing emissions from fossil fuels, and it is important that our net-zero systems reflect this physical reality.

That said, less durable solutions still have a role to play. ...

2024-11-11T15:02:47Z

In reply to nevent1q…g4tx
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That said, less durable solutions still have a role to play. Temporary removals such as afforestation/reforestation can counterbalance land use emissions, and temporary reductions of warming have real value in minimizing peak temperatures.

Our new paper provides further evidence that credible net-zero ...

2024-11-11T15:02:41Z

In reply to nevent1q…hedz
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Our new paper provides further evidence that credible net-zero commitments require a like-for-like approach: https://www.annualreviews.org/content/journals/10.1146/annurev-environ-112320-105050.

Given 100,000-year+ atmospheric lifetime fossil CO2, it can only be credibly neutralized by permanent carbon removal.

If CDR only has a durability of 100 years (e.g. much of the CDR ...

2024-11-11T15:02:35Z

In reply to nevent1q…9yv0
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If CDR only has a durability of 100 years (e.g. much of the CDR market today), it would result in 1.1C more warming by 2500 in a scenario that otherwise stabilizes warming below 2C. CDR with a >1000-year durability is required to stabilize global temperatures.

In the study, published today in Nature Communications, we ...

2024-11-11T15:02:25Z

In reply to nevent1q…6u9n
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In the study, published today in Nature Communications, we simulate the climate impact of 6 GtCO2 of residual CO2 emissions at the point of net-zero (the typical value in scenarios examined in the recent IPCC report) under different durability assumptions.

We need carbon removal in addition to deep emissions reductions ...

2024-11-11T15:02:14Z

We need carbon removal in addition to deep emissions reductions to get to net-zero. But as we show in a new study the durability of removals is key to ensure net-zero actually stabilizes global temperatures and meets our climate goals: https://www.nature.com/articles/s43247-024-01808-7

Climate change is one of the defining challenges of the 21st ...

2024-10-30T17:29:31Z

Climate change is one of the defining challenges of the 21st century. While individual actions can reduce impacts, gov't policy will play a big role to make clean energy cheap and widespread.

The most important climate action you can take today is to vote.

2024 is now virtually certain to be the warmest year on record, ...

2024-10-28T15:20:01Z

In reply to nevent1q…z7kp
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2024 is now virtually certain to be the warmest year on record, and will be above 1.5C in most surface temperature datasets, including Copernicus/ECMWF's ERA5 shown here:

Here is the latest projection of where October 2024 will end up, ...

2024-10-28T15:19:54Z

In reply to nevent1q…5yr2
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Here is the latest projection of where October 2024 will end up, based on data for the first 26 days of the month:

Daily global surface temperatures have been trending upward over ...

2024-10-28T15:19:46Z

Daily global surface temperatures have been trending upward over the past month, and are now back in record territory for the first time since early September.

While October is very unlikely to set a new record, it will be close to what we saw in 2023.

New UNEP emissions gap report highlights a "massive gap ...

2024-10-24T15:24:20Z

New UNEP emissions gap report highlights a "massive gap between rhetoric and reality" and calls for a "quantum leap" in ambition to deliver Paris goals, as the world is way off-track today.

I cover the details over at @CarbonBrief: https://www.carbonbrief.org/unep-new-climate-pledges-need-quantum-leap-in-ambition-to-deliver-paris-goals/

Enhanced weathering is a promising technology to permanently ...

2024-10-16T15:26:57Z

Enhanced weathering is a promising technology to permanently remove CO2 from the atmosphere, improve soil pH, agricultural yields, and reduce N2O emissions, but is challenging to verify.

After a year of work involving 50 scientist, we have a firm roadmap for verification: https://cascadeclimate.org/blog/foundations-for-carbon-removal-quantification-in-erw-deployments

With 9 months of the year now behind us, 2024 is virtually ...

2024-10-02T20:31:55Z

In reply to nevent1q…tquf
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With 9 months of the year now behind us, 2024 is virtually certain to beat 2023 as the warmest year on record:

September 2024 started out roughly as warm as 2023, but while ...

2024-10-02T20:31:46Z

In reply to nevent1q…f7l6
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September 2024 started out roughly as warm as 2023, but while last year saw a massive spike in temperatures after the first week of the month up to ~1.8C, 2024 remained more consistently around 1.5C:

Here is how this month compares to all the other months in recent ...

2024-10-02T20:31:24Z

In reply to nevent1q…dfyz
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Here is how this month compares to all the other months in recent years. Global temperature anomalies have fallen a bit since the start of the year, but have remained stubbornly around 1.5C above preindustrial levels ever since May 2024.

September 2024 was the second warmest September on record, coming ...

2024-10-02T20:30:54Z

September 2024 was the second warmest September on record, coming in just above 1.5C relative to preindustrial levels in the Copernicus/ECMWF ERA5 dataset.

It was a ~0.3C warmer than any September prior to 2023 (which set an extraordinary high bar):

One year after the Patrick Brown hullabaloo, Grist has a nuanced ...

2024-10-01T22:15:49Z

One year after the Patrick Brown hullabaloo, Grist has a nuanced profile covering the event and its aftermath: https://grist.org/science/patrick-brown-profile-climate-scientist-criticized-study/

Since the 1950s, there has been a strong increase in heavy ...

2024-09-30T22:18:07Z

In reply to nevent1q…lrh4
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Since the 1950s, there has been a strong increase in heavy precipitation across the contiguous US, with the largest increases in Northeast, Midwest, and Southeast. These changes have contributed to increases in river and stream flooding in these regions. https://nca2023.globalchange.gov/chapter/2/

As we noted in the US 5th National Climate Assessment: "There ...

2024-09-30T22:18:01Z

As we noted in the US 5th National Climate Assessment:

"There is robust evidence that human-caused warming has contributed to increases in the frequency and severity of the heaviest precipitation events across nearly 70% of the US."

Happy end of coal in the UK day, to all who celebrate! ...

2024-09-30T19:17:06Z

Happy end of coal in the UK day, to all who celebrate! https://interactive.carbonbrief.org/coal-phaseout-UK/

Both Sam Altman (OpenAI) and Dario Amodei (Anthropic) have made ...

2024-09-23T21:15:41Z

Both Sam Altman (OpenAI) and Dario Amodei (Anthropic) have made some version of the argument that AI will give us the power to "fix the climate". I find this a deeply problematic position, as the challenges of mitigation are as much political as technological.

With more than half of September 2024 now in, its clear that we ...

2024-09-19T05:06:46Z

With more than half of September 2024 now in, its clear that we will not be surpassing 2023's "gobsmackingly bananas" record warmth for the month.

However, it will still likely be ~0.3C warmer than any September on record prior to 2023:

Global temperatures have remained persistently high over the past ...

2024-09-09T16:31:08Z

Global temperatures have remained persistently high over the past few months despite fading El Nino conditions in the tropical Pacific. We saw records tied or set in May, June, July, and August.

Its only in September 2024 that we are likely to move out of record territory:

For more details, see the excellent work done by the Global ...

2024-08-14T22:26:44Z

In reply to nevent1q…964p
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For more details, see the excellent work done by the Global Carbon Project team on measuring both CO2 emissions and sinks over the years: https://globalcarbonbudget.org/

Today the natural CO2 emissions are actually negative, as land ...

2024-08-14T22:26:39Z

In reply to nevent1q…t6gf
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Today the natural CO2 emissions are actually negative, as land and ocean sinks are taking up more CO2 than they emit in response to humanity's perturbation of the climate system. We know both ocean and biosphere sinks are taking up much more CO2 than they are releasing.

This balance meant that until humans started digging up and ...

2024-08-14T22:26:31Z

In reply to nevent1q…72hr
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This balance meant that until humans started digging up and burning fossil fuel reserves that had remained undisturbed for millions of years, atmospheric CO2 remained unchanged. We know clearly humans are responsible for this increase due to the isotopic signal of fossil carbon.

I often see folks inaccurately say that human emissions are tiny ...

2024-08-14T22:26:25Z

In reply to nevent1q…6d2c
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I often see folks inaccurately say that human emissions are tiny compared to natural CO2 emissions. But natural net CO2 emissions are historically negligible; emissions of CO2 from biomass decay, respiration, or natural combustion are balanced by absorption from vegetation growth

Starting 250 years ago, we began putting lots of carbon that was ...

2024-08-14T22:26:11Z

In reply to nevent1q…hcsg
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Starting 250 years ago, we began putting lots of carbon that was buried underground for millions of years into the atmosphere. All in all we’ve emitted nearly 2 trillion tons of CO2 from fossil fuels, which is more than the total mass of the biosphere or all human structures:

The carbon cycle has been close to equilibrium through the ...

2024-08-14T22:26:03Z

The carbon cycle has been close to equilibrium through the Holocene; we know this because we measure atmospheric CO2 concentrations in ice cores. But in the past few centuries CO2 has increased by 50%, and is now at the highest level in millions of years due to human emissions.