• I was not suggesting that increased air conditioning load is unimportant, just that its small relative to the big physical climate feedbacks like water vapor and ice albedo.
• Permafrost emissions are not a major player in arctic amplification per se (though changing albedo from surface melt is), as any methane or CO2 from permafrost ends up being quickly well-mixed through the atmosphere.
Here are the major physical climate feedbacks, as well as the spread of uncertainty in each across our models. Values above zero are positive feedbacks, while those below zero are negative:
Overall, climate feedbacks amplify an expected ~1C warming per doubling CO2 into ~3C warming, with the water vapor feedback playing the largest role.
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We just published our State of the Climate Q2 update over at @CarbonBrief:
⬆️ Now a ~95% chance 2024 will be the warmest year on record.
⬆️ 13 month streak of records set between June 2023 and June 2024.
⬆️ July 22nd 2024 was the warmest day on record (in absolute terms).
⬇️ July 2024 will very likely come in below July 2023, breaking the record streak.
⬇️ The rest of 2024 is likely to be cooler than 2023 as El Nino fades and La Nina potentially develops.
⬇️ Second lowest Antarctic sea ice on record.carbonbrief.org/state-of-the-c…
The past 13 months have each set a new record, with 2024 being quite a bit warmer than 2023 (at ~1.63C above preindustrial levels) in the ERA5 dataset:
However, the margin by which records are being set has shrunk; global temperatures were setting new records by a stunning 0.3C to 0.5C in the second half of 2023, but have been breaking the prior records (set in 2016, 2020, or 2023) by only 0.1C to 0.2C this year:
Global surface temperatures from @BerkeleyEarth are now out for June. It was the warmest June on record for land, oceans, and the globe as a whole by a sizable margin (~0.14C), and came in at 1.6C above preindustrial levels. berkeleyearth.org/june-2024-temp…
This was the 13th consecutive record setting month, and the 12th month in a row above 1.5C:
The exceptional nature of recent global temperatures really stands out when we look at a 12-month moving average:
Global temperatures were extremely hot in June 2024, at just over 1.5C, beating June 2023's previous record-setting temperatures by 0.14C and coming in around 0.4C warmer than 2016 (the last major El Nino event).
Now 2024 is very likely to beat 2023 as the warmest year on record
June 2024 was so warm that – in the absence of 2023's exceptional warmth – it would have beaten any past July as the warmest absolute monthly temperature experienced by the planet in the historical record:
This plot shows how June 2024 stacked up against all the prior Junes since 1940 in the ERA5 dataset:
We’ve long talked about the carbon budget, but given that the world is on track to pass the 1.5C target in the coming decade its time to start talking about the "carbon debt".
Carbon dioxide accumulates in the atmosphere where it lasts for an extremely long time. While about half of our emissions are removed by land and ocean carbon sinks over the first century, it takes on the order of 400,000 years for nature to fully remove a ton of CO2.
But it turns out that the warming from our CO2 emissions is also extremely long lived. Even if global CO2 emissions ceased and atmospheric CO2 concentrations began to decline, the warming from those emissions would remain for millennia: pnas.org/doi/full/10.10…
Recently we've seen a vibrant debate on when the world will firmly pass 1.5C.
Over at @CarbonBrief I weigh in with a new analysis, finding that it will most likely occur in the late 2020s or early 2030s in a world where emissions do not rapidly decrease. carbonbrief.org/analysis-what-…
Global temperatures in any given year reflect short-term natural variability on top of longer-term human-driven warming. For example, a big El Niño or La Niña event can result in global temperatures up to 0.2C warmer or cooler, respectively, than they would otherwise be.
While there is no formal definition how the 1.5C goal is measured, it is generally interpreted to refer to long-term, human-driven warming.
For example, the IPCC uses the midpoint of a 20-year period as a way to avoid overinterpreting short-term natural variability.
There is something of a genre of very online individuals™ discovering stratospheric aerosol injection and proclaiming it as a low-cost solution to climate change. Spoiler alert: its not.
In this case the thread uses a bunch of my figures so its worth responding.
Climate change is driven primarily by our emissions of carbon dioxide. We've emitted a lot of CO2: around 2.5 trillion tons since 1750, or the weight of the the biosphere and everything humans have ever built combined theclimatebrink.com/p/the-staggeri…
This CO2 remains in the atmosphere for a long time; it takes well over 100k years for a ton of CO2 emitted today to be fully removed. The warming caused by CO2 also sticks around; a ton emitted today will continue to warm the planet for millennia: pnas.org/doi/full/10.10…