IPCC SCIENTIFIC REPORT SUMMARY.
Learn more about what’s in WGI AR6 - the latest climate science report from the Intergovernmental Panel on Climate Change.
I. The Current State of the Climate
The IPCC report is clear that:
Emissions from human activities have warmed the atmosphere, ocean and land. The scale of recent changes across the climate system are unprecedented.
One change in the new report:
It places greater emphasis on regional climate change and how current extreme events – the flooding, the heatwaves etc. – are linked to climate change, human-induced climate change.
This should serve as a signal to politicians, policymakers, the fossil fuel industry, and everyone in the system to make some massive changes.
One of the harder-hitting parts of the report:
The measurements of earth’s equilibrium climate sensitivity have improved a lot.
The report now gives a best estimate of equilibrium climate sensitivity of 3°C with a narrower range compared to the last report. The likely range is now between 2.5°C to 4°C where it was somewhere between 1.5°C to 4.5°C,
So, what does that mean?
It means we’re more likely to be a little worse off up than we thought. There is not as much room for error, and the climate system is not as likely to bounce back quite so easily.
II. Climate Scenarios
The IPCC report states that:
Global temperatures will continue to increase until at least the mid-century under all of the emissions scenarios.
And we will go over 1.5°C and 2°C during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the next couple of decades.
1.5 to 2°C is the range that almost every single nation signed up to under the Paris Agreement. But 1.5degrees is looking highly ambitious. Doable, but ambitious.
The world is already most of the way to 1.5, so:
There would need to be immediate, rapid and large scale reductions in emissions to limit warming to within that range.
One thing to note is that:
Under all the scenarios emissions go down to zero. The difference is really just a matter of effort and how long it’s delayed.
Possibly the most positive thing is that the future is still in our hands and the system has that ability to change.
III. Effects on the Climate System
The report makes it clear that:
With every bit of emissions the projected changes in extremes get larger in frequency and larger intensity. And that applies to every region of the world.
That could mean more frequent and intense:
Hot extremes, marine heatwaves. It is very likely that heavy precipitation events will intensify and become more frequent in most regions.
Some regions experience agricultural and ecological droughts, some will have more intense tropical cyclones, and we see reductions in Arctic sea ice, permafrost and snow cover.
These changes would be more widespread at 2°C than at 1.5°C of global warming and even more widespread and pronounced at the higher levels of warming.
In addition the report says that:
As emissions rise, the ocean and land carbon sinks that slow the accumulation of carbon dioxide in the atmosphere are projected to be less effective.
IV. System Recovery
Climate sensitivity and the system bouncing back
Not so good news:
Many changes from past and future emissions are not going to be reversed for centuries to millennia, especially when it comes to changes in the ocean, ice sheets and global sea level.
The report also mentions that:
Low-likelihood events that have potentially high impacts, like ice sheet collapse and abrupt ocean circulation changes are not off the table.
They are kind of worst case scenarios. But would have high risks for society and ecosystems.
V. Limiting Future Climate Change
The IPCC science is policy neutral, so they don’t give recommendations about what policies countries should follow. But it does indicate how the impacts are limited under each scenario.
All pathways that limit warming to 1.5°C by 2100 assume that:
In addition to immediate, large-scale emissions reductions - there will also be some form of carbon dioxide removal. Where humans remove carbon dioxide from the atmosphere and store it.
This could be through:
Nature -based solutions: like reforestation, land-use change and other ecosystem-based approaches. Or more industrial processes: like direct air capture or bioenergy with carbon capture and storage.
All scenarios go down to at least net zero carbon dioxide emissions. None of them, not even the high emission scenarios, assume no action. It’s just a matter of how hard and how fast we go.
IPCC Science
Fast Facts.
1. Emissions from humans have warmed the atmosphere
2. The changes are unprecedented
3. The current extreme events can be linked to climate change
4. Changes in extremes get more frequent and intense as emissions rise and more widespread and more pronounced.
5. Many changes are not likely to be reversed for centuries to millennia
6. Warming levels will go over 1.5 and 2 degrees unless there are immediate, rapid and large-scale emissions reductions
7. Plus some carbon dioxide removal
8. Positives: we have the ability and the tools to change
9. Under all projected scenarios, carbon dioxide emissions go down to at least net zero. It just depends how hard and fast it happens