The physical risks of climate change are not just looming in the future, but have already become very evident today. Projections of rising global temperatures in a recently released World Meteorological Organization report, along with observations from recent years, underscore that the climate system is not static but is moving towards ever greater extremes. . The 10 hottest years recorded with thermometers since recording began in 1880 (140 years ago) all occur in the past 16 years. These changes in patterns of global warming statistics are reflected at the regional level, as evidenced by the complete dominance of dark red “record hot” pixels over dark blue “record cold” (none) pixels in the regional temperature map of the United States. NOAA for 2020.
Additionally, the year 2020 (a La Niña year) roughly matched 2016 (an El Niño year) as the hottest year on record. Why is this a surprise? Because La Niña years are generally cooler and El Niño years are generally warmer than usual. La Niña and El Niño conditions, along with volcanoes (cooling) and other natural variations, add year-to-year variability to the otherwise monotonous global warming caused by greenhouse gases and other air pollutants.
As the surface warms, the Earth’s atmosphere is getting wetter and climate extremes more intense and frequent. Arctic summer sea ice is disappearing faster; the Greenland and Antarctic ice caps are retreating faster; tropical cyclones intensify and move more slowly, creating storm surges and more precipitation and more severe flooding; and droughts, extreme heat and forest fires are intensifying. These trends, at scales ranging from local to global, are now having an impact – and in the decades to come, are likely to have an additional impact – on vulnerable infrastructure, supply chains and human health, and induce famine and widespread migration.
There is now substantial evidence that achieving the aggressive long-term global goal of keeping the increase in global average surface temperature well below 2 degrees Celsius from its pre-industrial level will significantly reduce the physical risks posed by climate change. While the long-term goals of the Paris Agreement suggest that world leaders have taken these physical risks seriously, the short-term goals of the agreement are largely not on track to meet these long-term goals. long term without a substantial change of direction right now.
At the same time, efforts to move the world towards net zero emissions in line with the 2 degree Celsius target come with major new risks of local-to-global “transition” and associated challenges that need to be addressed. This transition involves changes on the political, social, technological and economic fronts, and presents new challenges for financing and economies, from stranded fossil fuel assets to stranded workers in need of retraining. We will need to find the optimal balance between the risk of short-term overinvestment in today’s green technologies that will eventually be replaced, and the risk of underinvesting in these technologies and subsequently having to reduce emissions rapidly. greenhouse gases with the resulting economic shocks.
Reducing these risks of transitioning to net zero emissions economies will involve the integration of physical and transient components, a process that requires new and improved models and frameworks. The goal is to enable decision-makers in government and industry to reduce transition risks as an integral companion to mitigation strategies. Financial institutions and regulators will also need to get involved. Finally, we will need to invest more and more in adaptation and mitigation to reduce global climate risks.
To frame future studies on physical and transition risks, MIT has just released 2021 Global Change Outlook provides probabilistic climate and socio-economic projections obtained using updated probability distributions for key parameters of human components. and the Earth system from our integrated modeling of the world system. (IGSM).
These projections provide insight into the likelihood of the outcomes of interest, including emissions, concentrations, temperature, precipitation, GDP, and energy. Outlook 2021 also presents prospects for achieving the short-term goals of the Paris Agreement (as defined by Nationally Determined Contributions, or NDCs) and the long-term goals of sustaining the global temperature rise. average below 2 degrees Celsius or even 1.5 degrees.
Finally, the solutions to these challenges must be affordable and equitable for all people and all nations. The poorest countries are the most vulnerable and the least responsible for climate change. And the COVID-19 pandemic superimposed on climate change has exposed the cumulative effects of multiple stressors on these same vulnerable populations.
Ronald prinn, Sc.D, is professor of atmospheric sciences at MIT and director of MITJoint Program on the Science and Policy of Global Change and the Center for the Science of Global Change. Prinn’s research interests integrate the chemistry, dynamics and physics of the atmospheres of Earth and other planets and the chemical evolution of atmospheres.