Zeke Hausfather: With four months of data now in from ERA5, we see a roughly 66% chance that 2024 will surpass 2023 as the warmest year on record – and a >99% chance it will be one of the top-two warmest years. The current best-estimate is that 2024 will come it at just above 1.5C:

With four months of data now in from ERA5, we see a roughly 66% chance that 2024 will surpass 2023 as the warmest year on record – and a >99% chance it will be one of the top-two warmest years. The current best-estimate is that 2024 will come it at just above 1.5C:

These estimates have not changed all that much as new data (and updated El Nino / La Nina forecasts) have come in, though the error bars have shrunk:

That being said, while the approach used to assess annual temperatures based on the first four months of the year and El Nino/La Nina state have been largely accurate in predicting past years, they pretty wildly missed the mark in 2023.

If factors that led to 2023 being warmer than expected persist, and global temperatures do not fall as the year progresses and El Nino fades and La Nina develops, than its possible we could see higher temperatures than currently forecast: www.theclimatebrink.com/p/warmest-ap...

Warmest April on record – but a possible return to predictability?www.theclimatebrink.com While temperatures in 2023 were "gobsmacking", 2024 is shaping up to be a more normal El Nino year

One expression is water vapor - increased non-linear in the marine boundary layer in 2012-2016 (SST's had been the driver) and again in 2023/24 - by an astonishing >6% (NOAA) Data. And tropical poleward water vapor transport is another driver of MHWs at higher latitudes- prevents latent heat release

And as we had from 2012 to 2016 a warming jump of ~0.4 (not in mean values, but absolute terms during that period) and a staggering warming jump of ~0.5°C the last 10 month the speed of warming reaches now critical levels...

And as we have now the tropical Atlantic and the Indian Ocean developing permanent marine heatwave stages we are now in a planetary emergency...

Add then a cloud feedback over warmer oceans, a wind feedback of declining wind speeds over warmer oceans, an increasing surface patter affect over the continents and oceans disturbing atmospheric circulations all add to these 5 stages...

First stage: increasing thermal stratification; second stage: marine heatwaves expand fast; third one ocean heat uptake to deeper layers is declining; fourth stage: ocean heat comes up again; fifth stage: water vapor feedback starts; sixth stage: overkill! The first 5 are happening parallel

This feedback is seen at the surface in the form of marine heatwaves increasing non-linear - if thermal stratification of the upper oceans breaches thresholds even more warming is accumulating in the upper ocean turning the wheel faster.

Wait now since two years that it starts as it is so obvious that heat needs more time to enter the deeper ocean than it is added in the surface layers leading to non-linear increases in thermal stratification which DID NOT HAPPEN IN PAST WARMING PHASES!

Slowly it comes now into the main stream media that a physical runaway climate warming feedback cascade is now being discussed behind the scenes - we warmed to oceans way too fast - ops the speed of warming triggers the worst kind of feedback cascade... www.nytimes.com/2024/05/07/p...

How Changing Ocean Temperatures Could Upend Life on Earthwww.nytimes.com Is the world’s climate close to a tipping point?

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