What Happens After Warming Hits 1.5C? A Guide to Climate Overshoot
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Progress toward a global clean-energy transition and general decarbonization is proceeding at a rate only dreamed of a decade ago. Falling costs for solar and wind energy, batteries and electric vehicles continue to push into the economy. Technologies and nature-based approaches that remove carbon dioxide directly from air are proven but remain expensive.
The most authoritative statements on how these efforts are doing come from the IPCC. A report in April, authored by hundreds of researchers and based on 18,000 studies, found that the amount of time left is small and shrinking. Emissions must peak before 2025, the IPCC wrote, meaning there are roughly 80 months left to have a 67% chance of staying under 1.5C. (To keep the 2C target, by contrast, there remains 24 years of CO₂ emissions left.)
Emissions, of course, are still rising. Few of the probable futures from here are compatible with stopping before the 1.5C limit is breached. Of 230 scenarios in the latest IPCC report that keep temperatures at or below 1.5 by 2100, 96% pass by that threshold in the near term before nascent carbon dioxide removal technologies kick in and warming eventually drops back down. That means we can still create a 1.5C compatible world, even if we break through that limit initially.
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In an overshoot scenario in which the global average temperature goes beyond 1.5C and humanity deploys costly technologies at scale to complement emissions reductions, the distance traveled over that line will become crucial. The UN Environment Program publishes an annual report showing how far actual emissions and trends remain from agreed-to limits. This year's Emissions Gap Report concludes that existing policies would bring an estimated 2.8C temperature rise. All of the Paris Agreement pledges made by nations, if fulfilled, would lead to an average estimate of 2.6C warming, according to Inger Andersen, UNEP executive director.
A best-case scenario would see nations fully implementing their UN pledges, net-zero goals and additional policies. That situation would “point to a 1.8C rise,” she writes in the forward to this year’s UNEP report. “However, this scenario is currently not credible.”
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https://www.bnnbloomberg.ca/what-happens-after-warming-hits-1-5c-a-guide-to-climate-overshoot-1.1843077Some nice abstract numbers but the effects they cause on the ground will be bad.
1,1C was enough to trigger the melt of Greenland and Antarctica. Every tenth of a degree extra will just accelerate this.
It was also enough to trigger the change of permafrost from sink to source. The added jump in temperatures will makes this worse and it will also increase the amount of rain which accelerates the melt.
On top of that there will be some arctic greening or browning. So more trees and shrubs will grow there which will not be good for the local albedo.
Current conditions are also enough to trigger Arctic ice loss by 2050 (from modelling) but going towards 1,5 should bring this forward.
We will lose glaciers all over the world etc.
What will the conditions be in the Horn of Africa or Australia at those temps?
How big will the rain events get at 1,5C?
And of course it also increases the chance of a multi bread basket failure.
It´s not going to help with forest fires in general and at some point lots of peatlands are at risk of drying out too.