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Zeke Hausfather@hausfath.bsky.social |
6400 followers 183 following 678 posts
"A tireless chronicler and commentator on all things climate" -NYTimes.
Climate research lead @stripe, writer @CarbonBrief, scientist @BerkeleyEarth, IPCC/NCA5 author.
Substack: theclimatebrink.substack.com/
Twitter: @hausfath
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Zeke Hausfather
@hausfath.bsky.social
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This is an electoral platform I could get behind in the US: a left that builds. Though for better or worse, a lot of these (e.g. planning/zoning) are primarily state rather than federal responsibilities in the US.
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Zeke Hausfather
@hausfath.bsky.social
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Yep, final two weeks of the month.
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Zeke Hausfather
@hausfath.bsky.social
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Here are how the projections of 2024 have evolved as each new month of data has come in. The unusually high June temperatures played a big role in pushing up the projections for the full year:
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Zeke Hausfather
@hausfath.bsky.social
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Finally, with the first six months of data in for the year, I now estimate that there is an approximately 95% chance that 2024 beats 2023 to be the warmest year since global surface temperature records began in the mid-1800s:
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Zeke Hausfather
@hausfath.bsky.social
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Finally, if we look at the daily temperatures, we see that June started off exceptionally warm, but cooled down a little bit in the final two weeks of the year. If it stays around current levels, we should see 2024 finally fall below 2023's extremes in the month of July.
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Zeke Hausfather
@hausfath.bsky.social
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This plot shows how June 2024 stacked up against all the prior Junes since 1940 in the ERA5 dataset:
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Zeke Hausfather
@hausfath.bsky.social
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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:
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Zeke Hausfather
@hausfath.bsky.social
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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
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Zeke Hausfather
@hausfath.bsky.social
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As far as I’m aware, all states will include the democratic nominee (as the convention has yet to occur). Otherwise if (god forbid) a candidate died their opponent would automatically win the election, which would be problematic!
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Zeke Hausfather
@hausfath.bsky.social
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Yep, though the first 80% or so is in the first 1000 years. However, because the oceans are still heating up the warming from CO2 emitted today persists relatively unchanged for millennia even as concentrations decline.
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Zeke Hausfather
@hausfath.bsky.social
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I generally steer clear of politics here, but sometimes there are moments when things need to be said. Biden is too old to run an effective campaign for president at this point. For the good of the country, he should step aside for someone younger and more fit to meet the moment.
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Zeke Hausfather
@hausfath.bsky.social
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I'll do better, I'll write a whole article that includes figures and links to the sources... 🙄www.nature.com/articles/climate.2008.122
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Zeke Hausfather
@hausfath.bsky.social
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But to your question, the amount of heat we are talking about is so vast there is no real way to "move" it (and CO2 in the atmosphere keeps trapping heat in the system, so we would have to keep moving it for millennia). See the discussion of geoengineering in my piece, for example.
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Zeke Hausfather
@hausfath.bsky.social
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But the point is that no matter how one does it, the only way to ultimately reverse global warming is to remove CO2 from the atmosphere that we have previously emitted. And, of course, none of that matters unless we can get on track for zero emissions!
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Zeke Hausfather
@hausfath.bsky.social
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Well, CCS does not remove CO2 from the atmosphere unless what you are capturing is biogenic (as in BECCS). You'd need something like direct air capture, enhanced rock weathering, or ocean alkalinity enhancement.
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Zeke Hausfather
@hausfath.bsky.social
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And if we ever want to bring temperatures back down when we finally get to zero CO2 emissions, we need to actively reduce the amount of CO2 in the atmosphere by taking the we’ve previously emitted CO2 back out and keeping it out for millennia. This is the carbon debt.
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Zeke Hausfather
@hausfath.bsky.social
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In other words, even if we stopped all emissions today, the world would not cool down substantially for many millennia to come.
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Zeke Hausfather
@hausfath.bsky.social
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The implications of this are stark and broadly under-appreciated outside of the climate science community. The warming the world experiences is in essence a largely time-invariant function of our cumulative CO2 emissions.
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Zeke Hausfather
@hausfath.bsky.social
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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: www.pnas.org/doi/full/10....
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Zeke Hausfather
@hausfath.bsky.social
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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.
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Zeke Hausfather
@hausfath.bsky.social
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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".
My latest piece over at The Climate Brink: www.theclimatebrink.com/p/the-growin...
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Zeke Hausfather
@hausfath.bsky.social
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More or less. But it also turns out that warming from non-CO2 GHGs more or less cancel our cooling from aerosols, so if you set all emissions to zero you get roughly flat temperatures:
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Zeke Hausfather
@hausfath.bsky.social
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Though to be fair, only a small fraction of sulfur emissions are from bunker oil:
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Zeke Hausfather
@hausfath.bsky.social
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NASA finally launched the PACE satellite (the first one blew up years ago), which should provide some good data here. It won't eliminate uncertainties (as indirect effects on cloud formation are hard to constrain), but it should help.
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Zeke Hausfather
@hausfath.bsky.social
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Yes, if we stopped all aerosol emissions but kept all other emissions. But given that a lot of aerosol emissions are a byproduct of fossil fuel use that would be a somewhat weird scenario.
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Zeke Hausfather
@hausfath.bsky.social
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It’s very much an outlier in the literature. If you have dozens of ECS studies each year you will inevitably have ones unusually low or high. But we also know an ECS that large would run away to snowball earth in the last ice age so 🤷
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Zeke Hausfather
@hausfath.bsky.social
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No, we’ve caused 1.3C warming. Where we go from here depends on our CO2 emissions, but also the balance of aerosols and short-lived climate pollutants like methane. To a first order approximation, warming from methane balances out cooling from aerosols.
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Zeke Hausfather
@hausfath.bsky.social
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Aerosols mostly refers to sulfur dioxide. Nothing to do with consumer products.
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Zeke Hausfather
@hausfath.bsky.social
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A few days in the lower atmosphere (where they are all emitted today outside of particularly explosive volcanic eruptions).
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Zeke Hausfather
@hausfath.bsky.social
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These figures use the FaIR model, and were lightly adapted (and updated) from @chrisroadmap.bsky.social's work. You can find the code to generate them here: github.com/chrisroadmap...
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Zeke Hausfather
@hausfath.bsky.social
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The uncertainty in the effect of aerosols on the climate is also correlated with another major uncertainty: how sensitive the climate is to our emissions. Here is the range of sensitivity and aerosol forcing used in the analysis above, and their relationship:
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Zeke Hausfather
@hausfath.bsky.social
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The magnitude of cooling associated with our emissions of sulfur dioxide and other aerosols is one of the largest uncertainties in the climate system, and has large implications on how much warming we will experience in the future as we clean up pollution and emissions decline:
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Zeke Hausfather
@hausfath.bsky.social
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The world has warmed around 1.3C since the mid-1800s. Effectively all of this warming is due to emissions of CO2 and other greenhouse gases. But we'd have experienced substantially more – ~0.6C (0.2C to 1.2C) – if planet-cooling aerosols were not masking part of that warming:
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Zeke Hausfather
@hausfath.bsky.social
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Here is a version of that figure: essd.copernicus.org/articles/16/...
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Zeke Hausfather
@hausfath.bsky.social
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Yep, each year from 1850 through 2023.
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Zeke Hausfather
@hausfath.bsky.social
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We often focus on global temperatures, but land regions where we all live have been warming much faster. For #showyourstripes day, here are land, ocean, and global climate stripes shown on the same color scale:
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Zeke Hausfather
@hausfath.bsky.social
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They almost certainly will. Just not as fast as some of us were hoping. It’s still a bit to be determined what the anomalies of 2023 and 2024 mean for projections going forward.
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Zeke Hausfather
@hausfath.bsky.social
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We will closely be watching what happens to global temperatures over the next few months as El Nino fades and La Nina conditions start to develop. As @climateofgavin.bsky.social noted in Nature earlier this year: nature.com/articles/d41...
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Zeke Hausfather
@hausfath.bsky.social
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Finally, here is the evolution of daily temperatures so far in 2024 compared to 2023 and prior years. While there was a brief period where temperatures this year fell below 2023's levels, they have remained persistently hot.
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Zeke Hausfather
@hausfath.bsky.social
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Here is my latest projection for June 2024 temperatures compared to all the prior Junes in the ERA5 record. There's now a >95% chance that this year will set a new record based on the past relationship between the first 15 days of the month and the ultimate monthly temperature.
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Zeke Hausfather
@hausfath.bsky.social
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With half the month now behind us, June 2024 is very likely to be the warmest June on record. It is on track to beat 2023's record by nearly 0.2C, and may represent an ominous sign that global temperatures are not falling very quickly despite the fading of El Nino conditions.
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Zeke Hausfather
@hausfath.bsky.social
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Have a spare bike? 😉
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Zeke Hausfather
@hausfath.bsky.social
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Heading over to Oxford, UK, this week for a conference. Let me know if you are around and want to grab a pint!
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Zeke Hausfather
@hausfath.bsky.social
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A little bird told me.
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Zeke Hausfather
@hausfath.bsky.social
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Mostly a ramp up of planet cooling aerosols counterbalancing warming.
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Zeke Hausfather
@hausfath.bsky.social
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For more, check out the full analysis here: www.carbonbrief.org/analysis-wha...
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Zeke Hausfather
@hausfath.bsky.social
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There is no single best way to assess when the world will likely pass 1.5C. But both Carbon Brief’s approach and those of other groups all agree it will most likely happen in the late 2020s or early 2030s in a world (SSP2-4.5) where global emissions remain around current levels.
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Zeke Hausfather
@hausfath.bsky.social
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@copernicusecmwf.bsky.social, using a linear regression over the past 30 years, finds a slightly later date of 2033. The difference between the regression and climate models-based approaches reflect an expectation of modest near-term acceleration in models: cds.climate.copernicus.eu/apps/c3s/app...
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Zeke Hausfather
@hausfath.bsky.social
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These new estimates are broadly in-line with others in the literature. For example, the IPCC AR6 assessed warming projections estimate that global temperatures will pass 1.5C in 2031 in a SSP2-4.5 scenario:
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Zeke Hausfather
@hausfath.bsky.social
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This means if a different temperature record where "right", you would get a different range of exceedance years. For Berkeley Earth, for example, we would expect the world to pass 1.5C around 2027, and potentially even as early as 2025:
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