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Zeke Hausfather Profile picture
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30 Apr, 4 tweets, 2 min read
Skepticism is the heart of science, but needs to be informed skepticism. We shouldn't blindly follow experts, but should acknowledge our own biases and preconceptions when encountering new evidence.

This video by @neilhalloran strikes a perfect balance:
Also the data visualization is simply gorgeous. I'm more than a little professionally jealous!
I will make one criticism: the warming scenario he labels "current course that assumes we make no new efforts to reduce emissions" is not, in fact that. It was designed as the 90th percentile of possible outcomes in a world with no new policies after 2005. nature.com/articles/d4158…
Today our current policies put us on track for much less warming, thankfully, but we still have a long way to go to meet Paris Agreement goals:

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More from @hausfath

Zeke Hausfather Profile picture
30 Apr
Had a good discussion today on @TheWorld with @ProfTimJackson about the extent to which we can both have economic growth and mitigate climate change.

pri.org/file/2021-04-3…

Lets dig into the debate in a quick thread: 1/18
First, there are a lot of places where Tim and I agree. We agree on the need to replace fossil fuels with clean energy, and to get emissions down to zero. We agree GDP is a poor proxy for human wellbeing, and that modern economies have huge problems with inequality. 2/
Where we differ is on whether technology allows us to "decouple" economic activity from its environmental impact. 3/
Read 18 tweets
Zeke Hausfather Profile picture
29 Apr
How much warming is committed, "locked in", or "in the pipeline" has long been a source of confusion.

In a new @CarbonBrief explainer we take a deep dive into what would happen to the climate once we reach net-zero emissions.

A thread: 1/19
carbonbrief.org/explainer-will…
Much of the confusion around committed warming comes from a conflation of two different scenarios: one where atmospheric CO2 is held at constant levels (say, ~414 ppm today), and one where all our emissions go to zero. 2/
Until the mid-2000s, many climate models were unable to test the impact of emissions reaching zero. This is because they did not include biogeochemical cycles – such as the carbon cycle – and could not effectively translate emissions of CO2 into atmospheric CO2 concentrations. 3/
Read 20 tweets
Zeke Hausfather Profile picture
26 Apr
Last week the folks at @SwissRe released a report suggesting global losses of up to 14% of global GDP by 2050 due to warming expected in a current policy world.

Unfortunately, the way they use climate models is a bit problematic: swissre.com/institute/rese…

A thread: 1/13
First, credit where credit is due. The report focused on the RCP4.5 scenario in line with current policy projections from folks like @climateactiontr rather than the increasingly implausible RCP8.5 pathway: 2/
However, they then suggest that 2050 temperature outcomes under RCP4.5 would likely be 2C (50th percentile) to 2.6C (95th percentile) based on climate models used in the IPCC 5th Assessment Report. Its here that the problem arises. 3/
Read 14 tweets
Zeke Hausfather Profile picture
22 Apr
The US has committed to an ambitious goal of reducing emissions by 50% to 52% in 2030 relative to 2005 levels. In a new analysis, we look at what we are on track for today, and the additional reductions that would be needed to meet the new goal: thebreakthrough.org/issues/energy/… 1/16
The US has reduced its CO2 emissions by about 20% since 2005. However, nearly all those reductions have been concentrated in the power sector. If current trends continue, we expect US CO2 emissions to be around 30% lower than 2005 levels in 2030: 2/
In this current-trends-continue scenario, electric power sector emissions will fall 60% by 2030 compared to 2005 levels. Residential emissions will fall 18%, transportation emissions 15%, industrial emissions 5%, and commercial emissions will increase by 14%. 3/
Read 16 tweets
Zeke Hausfather Profile picture
6 Apr
In a new analysis, we find there are now 32 countries that have absolutely decoupled economic growth from CO2 since 2005. In these places both territorial emissions and consumption emissions (which include CO2 imported in goods) are falling. thebreakthrough.org/issues/energy/…
A thread: 1/21
Absolute decoupling has long been controversial, with some arguing that economic growth is fundamentally incompatible with emissions reductions. However, around 15 years ago things began to change. 2/
Rather than a 21st century dominated by coal that energy modelers foresaw, global coal use peaked in 2013 and is now in structural decline. We have succeeded in making clean energy cheap, with solar power and battery storage costs falling 10-fold since 2009. 3/
Read 26 tweets
Zeke Hausfather Profile picture
2 Apr
There are reasonable criticisms of too much reliance on assumed future carbon removal, and real barriers to scaling. At best it can offset a long tail of hard to decarbonize emissions and recover from overshoot.

But ruling out large-scale NETs makes 1.5C almost impossible. 1/6
The math of the 1.5C target is brutal, since we are already at between 1.2C and 1.4C today. Either all global emissions need to go to zero in the next 10-20 years, or you need to use large-scale net-negative emissions – as nearly all emissions scenarios used by the IPCC do: 2/6
Natural climate solutions can certainly get us some of the way there. But there are limits to how far they can scale, and real questions about permanence of biological carbon stores in a warming (and fire-prone) world. 3/6 carbonbrief.org/analysis-how-n…
Read 8 tweets

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