Climate scientist, IPCC/NCA5 author, temperatures, carbon removal, mitigation/energy systems. Climate research lead at Stripe, also Carbon Brief and Berkeley Earth.
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2026-07-28T10:08:46Z Event JSON
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Last Notes npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather In a UN speech today, President Trump said that "all of these [climate] predictions were wrong". npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather August 2025 was the third warmest August on record after 2023 and 2024 at approximately 1.3C above preindustrial levels. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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! npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather "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" npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather Sagan really got the fundimental challenge of longer-term problems like climate: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather "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." npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather The latest version of the Senate's BBB is a death sentence for US energy leadership and a giant gift to China. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather it is. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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): npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather We've released the Berkeley Earth temperature update for January 2025: https://berkeleyearth.org/january-2025-temperature-update/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather Scientists developed the first climate models in the late 1960s (for which the Nobel Prize in physics was recently awarded!). npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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). npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather yes, as far as we can tell: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021RG000757 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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." npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather Is limiting the temperature increase to 1.5°C still possible? Yes, but only in a model. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather Here is the latest projection of where October 2024 will end up, based on data for the first 26 days of the month: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather With 9 months of the year now behind us, 2024 is virtually certain to beat 2023 as the warmest year on record: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather As we noted in the US 5th National Climate Assessment: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather Happy end of coal in the UK day, to all who celebrate! https://interactive.carbonbrief.org/coal-phaseout-UK/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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/ npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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. npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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 npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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: npub1smxvkja7p7znk8kef8xc3cs8aacs40zq2sma2zd8fmvf78pr0c2q2ksjc0 Zeke Hausfather 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.
