Zero In On: A new generation of climate models, COVID-19 and the Paris Agreement

COVID-19 gives us a chance to slow down global warming and avoid the most dangerous climate change through a green economic recovery.  We must seize this opportunity to reset our climate future.

With global temperatures now almost 1.2°C above pre-industrial levels, limiting temperature rise to 1.5°C in line with the Paris Agreement means taking urgent and decisive global action.  Without it, and especially as COVID-19 has had virtually no direct impact on the climate, we still face the prospect of rising temperatures and more extreme climate impacts.

But our new report shows that slowing down global warming can be combined with tackling the economic crisis caused by COVID-19: a green recovery could cut the rate of temperature rise by up to half, giving us vital time and space over the next few decades to plan for and adjust to whatever impacts do come our way.  It would also give us a good chance of staying within 1.5˚C of warming, and meeting the Paris Agreement.

The report showcases recent work by the CONSTRAIN project, an international research consortium including many Intergovernmental Panel on Climate Change (IPCC) authors.  CONSTRAIN has been using the latest climate science to see how, as the world continues to navigate the COVID-19 pandemic, we can still avoid dangerous climate territory.


What do the latest climate models tell us?

The latest climate models, which are part of the modelling exercise known as CMIP6, are improving our understanding of the climate system in many ways.  They also suggest that if atmospheric CO2 concentrations double from pre-industrial levels, temperatures will rise by between 1.8 and 5.5°C.

This range is larger, and reaches higher, than that of previous modelling exercises as well as a recent authoritative study on the subject.  There has been much debate about the CMIP6 models at the higher end as they also produce higher end-of-century temperature projections than we might expect.

We looked at how the CMIP6 models recreate recent temperature change, and how this compares to actual temperature records.  The CMIP6 models with higher future temperature projections also overestimate how temperatures have changed in the recent past, suggesting that their higher-end future projections are unlikely (although not impossible).

This in turn helps us to understand which of the new models best reflect how the world might warm, depending on our future choices – and these choices, along with the resulting greenhouse gas emissions, are still by far the biggest influence on how much warming the models project.

What about the Paris Agreement and keeping warming below 1.5°C?

As the full impact of CO2 concentrations doubling would only be seen on timescales of centuries, once the climate system has had a chance to reach equilibrium, when it comes to avoiding dangerous climate change we need to focus on the next few decades.

In doing so, we need to understand what the Paris Agreement is about: global, human-induced temperature change, measured using the same approach on which the Agreement was originally based.  This is important because as soon as temperatures cross a 1.5°C threshold in any one place or in any one year, there is a danger that it’s seen as a “failure” of the Paris Agreement, discouraging the climate ambition we need.

But the global climate varies naturally year-to-year, and tracking the Paris Agreement means establishing the human signal above the natural background climate “noise”, looking at average temperature change over several decades.  As a result, we’ll only know that we’ve crossed into dangerous climate territory when we look back and realise that we’re already there.  So, carrying on as usual post-COVID is not an option.

How can COVID-19 recovery packages tackle climate change?

Combining model results with real-world measurements of natural climate variability shows that cutting emissions hard and fast as part of a green economic recovery, investing 1.2% of GDP in green technologies and industries, whilst refusing to bail out fossil fuel companies, can both halve global emissions by 2030, and slow down global warming by up to half its current rate in coming decades

This would not only get us on track for net-zero by mid-century but also give us a good chance of keeping temperature rise below 1.5°C.

We often focus on the total amount of warming we might end up with, but the latest models have helped us to see that strong and decisive climate action can also cut warming rates in the near future, allowing more time and space to cope with any inevitable climate impacts as we get on track to meet the Paris Agreement.

From ambition to action

Many governments around the world realise that ambitious and fundamental change is needed to tackle the climate crisis.  With the US re-entering the Paris Agreement, and more and more countries setting net-zero emissions targets for mid-century, things are looking hopeful. But current global ambition is not enough and several key players still aren’t on board.

Moreover, climate targets need to translate into action, and these efforts joined up with the vast sums being invested in COVID-19 economic recovery packages.  Otherwise, fossil-fuelled recoveries that push 1.5°C further out of reach can’t be ruled out.

With the fifth anniversary of the Paris Agreement just having passed, we now head further towards COP26, the crucial climate summit delayed by COVID-19 to November 2021.   The science tells us that slowing down warming, and avoiding the most dangerous climate change, is still very much on the table – but only just.

Political decisions taken now will determine whether we take that path, or choose one that crosses 1.5°C warming, moving from climate crisis towards climate catastrophe.

Further information:

The full report is: CONSTRAIN (2020) ZERO IN ON: A new generation of climate models, COVID-19 and the Paris Agreement. The CONSTRAIN Project Annual Report 2020, DOI:10.5281/zenodo.4282461.

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