Extreme Temperature Diary- Saturday December 20th, 2025/Main Topic: 2026 and 2027 Global Average Temperature Forecasts From Zeke Hausfather – Guy On Climate
Dear Diary. A few days ago, we got our first global average temperature forecast for 2026 from U.K.’s Met Office, suggesting that it will be near that of 2025 at between +1.29C to +1.53C higher than preindustrial conditions. Let’s round that figure off to +1.4C. Today I noticed a second opinion from Dr. Zeke Hausfather in my Gmail in box.
Zeke Housefather’s forecast is similar with an addition of a forecast for 2027. These forecasts mostly depend upon ENSO behavior and similar global volcanic activity that we see during 2025. Here is his summary:
My 2026 and 2027 global temperature forecastsThe best thing about predicting the near future is you don’t need to wait long to be wrong Tis the season for global temperature forecasts. The UK Met Office recently released their 2026 prediction, estimating that it is most likely to end up as the second warmest year on record at 1.46C (with a range of 1.34C and 1.58C) relative to the 1850-1900 preindustrial baseline period.¹ This is likely warmer than both 2023 and 2025² and with a small chance of being warmer than 2024.
Not to be outdone, James Hansen released his estimate that 2026 temperatures will also be around 1.47C in the GISTEMP dataset (albeit using a somewhat different 1880-1920 baseline)³, with the 12 month average dipping down to around 1.4C in the coming months before rising back up by year’s end.
Hansen also adds a prediction for 2027 at 1.7C (1.65C to 1.75C), albeit with the caveat that this refers to the peak 12-month warming during the year rather than the annual average. The prediction is based on an assumed El Nino developing in late 2026 – something that models have suggested is increasingly likely in recent weeks.
I’ve long done year-ahead predictions of global mean surface temperatures (included in the Carbon Brief annual state of the climate report). I base it on a linear regression model that uses a year count, the prior year’s temperature, the latest monthly temperature, and the predicted ENSO (El Nino / La Nina) conditions of the first three months of the coming year, as these factors tend to be the most predictive historically.
The model is fit on historical data since 19704 using the WMO average of six datasets,5 and I’ve slightly tweaked the model this year to include a squared term for the year count to ensure it is not forced to be too linear (though the effects of this change are minor).
For 2026 I expect global temperatures to be around around 1.41C, with a 95% confidence interval of 1.27C to 1.55C. This means that it is almost certain to be one of the top-4 warmest years, but quite unlikely to exceed 2024’s record. Global temperatures in 2026 will be slightly suppressed by modest La Nina conditions in the tropical Pacific early in the year, while a late-developing El Nino (if it occurs) will primarily affect 2027 temperatures.
 This model generally does a good job at predicting past calendar years using the same set of predictors (e.g. no actual data from the year except for Jan-March ENSO state). We can see this if we extend the hindcast back to 1970, where all years are within the model envelope with the exception of 1992 (when Pinatubo’s eruption resulted in significant unexpected cooling) and 2023 (which remains a bit of a mystery).
 Predicting temperatures two years ahead is a bit more of a challenge. Here I’ve adopted a somewhat different approach of using the current warming level and the rate of warming (0.27C/decade) that we estimated in the Forster et al 2025 paper as a starting point. I’ve further assumed a boost of 0.1C in global mean surface temperatures from an assumed moderately strong El Nino event in the central estimate, though the error bars encompass no El Nino (0C boost) to a very strong El Nino (0.15C boost).
This gives a central estimate of 1.57C for 2027, albeit with error bars wide enough to ride an elephant though (1.30C to 1.76C!) given the difficulty of accurately predicting ENSO state that far into the future.
 My central estimate of 1.57C is a bit lower than Hansen’s 1.7C, in part because I’m assuming a moderately strong El Nino and somewhat lower warming rates (0.27C/decade in Forster et al) then the 0.31C/decade that Hansen assumes. But his estimates remain within my (admittedly large) prediction error bars.
 The fun part about making these short term forecasts is that we won’t have to wait that long to see how well they play out. The less fun part is that we are all forecasting a future rate of warming well above the ~0.2C per decade that has characterized the post-1970 period.
1 Here the Met Office is using the WMO average of six datasets rather than just HadCRU5.
2 Note that final 2025 temperatures are not available yet, so annual values are estimated based on data through November. You will have to wait until January 12th to see the final values.
3 Somewhat conveniently, Hansen’s GISTEMP-based estimate using an 1880-1920 baseline gives values quite similar to what the WMO average of datasets gets using an 1850-1900 baseline, so its comparable to all the other forecasts in this piece without requiring any fancy adjustments.
4 Excluding 1982 and 1992 from the training data due to large volcanic eruptions. I’m not trying to predict major volcanic eruptions.
5 The WMO average includes NOAA, NASA, Hadley, Berkeley Earth, ERA5, and JRA-3Q.
Here are some “ETs” recorded from around the planet the last couple of days, their consequences, and some extreme temperature outlooks, as well as any extreme precipitation reports:
bing bang
Lots more records at Guy's place
Monthly global climate data update from @metoffice.gov.uk HadCRUT5 for the month of November 2025.
Third hottest month of November since 1850.
#climate
datagraver.com/climate-data... — Datagraver (@datagraver.com) 2025-12-19T11:53:29.334Z
Monthly global climate data update from Berkeley Earth for the month of November 2025.
Third hottest month of November since 1850.
#climate
datagraver.com/climate-data... — Datagraver (@datagraver.com) 2025-12-16T22:00:36.009Z
From there on it will get ugly fast as it will be as much a result of strengthening feedbacks as the jump will further reinforce all the feedbacks now coming into motion...
#Climate #Earth — (@umsonst.bsky.social) 2025-12-20T09:50:32.922Z
Hansen says 2027: — Climate News (@climatenews.bsky.social) 2025-12-20T20:53:11.873Z
How #climate breakdown is putting the world’s food in peril – in maps and charts
#environment #FoodSecurity — Robyn D (@koparafallskid.bsky.social) 2025-12-19T01:10:22.891Z
Friday from the American Meteorological Society concerning the government announcement of the closing of the National Center for Atmospheric Research (NCAR): — Richard Heatwave Berler (@heatwavekgns.bsky.social) 2025-12-19T21:37:50.292Z
We’re all at risk if Trump dismantles this legendary lab.
Breaking up the National Center for Atmospheric Research would be a "genuinely shocking self-inflicted wound."
grist.org/climate/were...
#Climate #Environment — Tory Stephens (@torystephens.bsky.social) 2025-12-18T20:02:10.204Z
This Yglesias piece in the NYT is horrifically bad. Almost every "fact" it cites is provably false. At best it is cocktail party banter from a pundit who knows nothing of energy. At worst, it was cut/paste from oil industry talking points. So, a rebuttal: www.nytimes.com/2025/12/18/o... — Sean Casten (@seancasten.bsky.social) 2025-12-20T14:57:15.767Z
The New York Times knows this is disinformative fossil fuel industry propaganda but published it anyway. This (via @amywestervelt.bsky.social) might have something to do with it:
drilled.media/news/drilled... — Michael E. Mann (@michaelemann.bsky.social) 2025-12-20T16:04:10.893Z
Did you know climate work attracts Katharines? 116 of us on Bluesky alone!
(This pack includes all creative spelling variations although the original has two A’s, deriving from the Greek καθαρός 😊)
This is Day 8 of my 20 days of Climate Starter Packs. For the previous entries please see below ⬇️ — Katharine Hayhoe (@katharinehayhoe.com) 2025-12-20T16:16:36.237Z
Dreaming of a White Christmas is as close to a White Christmas most will get this year.
You know it’s bad when #Florida has as much snow ❄️ on the ground as South Dakota. 😂
This Christmas it appears the US may have its lowest snow cover on record! — Jeff Berardelli (@weatherprof.bsky.social) 2025-12-20T16:26:46.776Z
“Last year more than 40% of electricity generation on Christmas Day came from renewables. It stood at 1.7% in 2009” #GreenSky #GreenShoots
“An extra 2 gigawatts of #wind and 3GW of #solar power came on to the network in 2025” @katharinehayhoe.com @350.org
www.theguardian.com/environment/... — Tim Morton (@timmorton2.bsky.social) 2025-12-20T19:26:01.060Z
Researchers at Tokyo University of Science showed that sodium-ion batteries with hard carbon anodes can charge faster than lithium-ion batteries by using a diluted electrode method that reveals sodium insertion is intrinsically quicker than lithium.
www.pv-magazine.com/2025/12/19/r... — Dr Paul Dorfman (@drpauldorfman.bsky.social) 2025-12-20T17:14:14.394Z
Chart: Clean energy remains dominant in the US — despite Trump.
www.canarymedia.com/articles/cle... — Dr Paul Dorfman (@drpauldorfman.bsky.social) 2025-12-20T17:12:31.060Z
United Kingdom added 2.5 GW of new deployed solar capacity in the first 11 months of 2025
www.pv-magazine.com/2025/12/19/u... — Dr Paul Dorfman (@drpauldorfman.bsky.social) 2025-12-20T17:13:36.646Z
Good grief ...
Trump bets on #nuclear fusion hype politi.co/4oYAnOr via @politico — Dr Paul Dorfman (@drpauldorfman.bsky.social) 2025-12-20T10:11:20.241Z
Paris fighting pollution and improving public health.
-No diesel cars from 2024
-100% #cleanenergy buses by 2025
-No petrol cars from 2030
-improving bike and pedestrian infrastructure.
We have the solutions, implement them. #ActOnClimate
#climate #energy #GreenNewDeal — Mike Hudema (@mikehudema.bsky.social) 2025-12-17T19:07:03.315Z
Students in the #Netherlands built this #solar-powered camper van. It can travel up to 740km a day - while powering a laptop, TV and coffee-maker.
We have so many solutions. Implement them. #ActOnClimate
#ClimateAction #ClimateCrisis #climate #energy #renewables #GreenNewDeal — Mike Hudema (@mikehudema.bsky.social) 2025-12-18T19:07:44.567Z
‘Everything is hanging by a thread’: Holding the line for Vancouver Island’s ancient trees.
As RCMP crackdowns intensify, forest defenders say the fight is about stopping #oldgrowth logging before it’s too late.
The latest from @brandimorin.bsky.social:
ricochet.media/climate/ever...
#climate — Ricochet Media (@ricochetmedia.bsky.social) 2025-12-17T23:17:04.636Z
Alexis Rockman Traces the Unsettling Evolution of a #Climate in Crisis #Art #Paintings
Link for more eerie #climatecrisis paintings and info: www.thisiscolossal.com/2025/12/alex... — Catherine (@shadowdogdesigns.bsky.social) 2025-12-18T19:51:29.224Z
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