As the first Pandemic of the Anthropocene grips the planet, a new study looking at the most likely path climate change will follow makes the COVID-19 pandemic look like a minor side effect, and a relatively benign side effect, compared to what’s probably in store for future generations.
An analysis finds the most likely range of warming from doubling carbon dioxide to be between 4.1 to 8.1 degrees Fahrenheit.
By Andrew Freedman and Chris Mooney
The current pace of human-caused carbon emissions is increasingly likely to trigger irreversible damage to the planet, according to a comprehensive international study released Wednesday. Researchers studying one of the most important and vexing topics in climate science — how sensitive the Earth’s climate is to a doubling of the amount of carbon dioxide in the atmosphere — found that warming is extremely unlikely to be on the low end of estimates.
These scientists now say it is likely that if human activities — such as burning oil, gas and coal along with deforestation — push carbon dioxide to such levels, the Earth’s global average temperature will most likely increase between 4.1 to 8.1 degrees Fahrenheit (2.3 and 4.5 degrees Celsius). The previous and long-standing estimated range of climate sensitivity, as first laid out in a 1979 report, was 2.7 to 8.1 degrees Fahrenheit (1.5 to 4.5 Celsius).
If the warming reaches the midpoint of this new range, it would be extremely damaging, said Kate Marvel, a physicist at NASA’s Goddard Institute of Space Studies and Columbia University, who called it the equivalent of a “five-alarm fire” for the planet.
The new range is narrower than previous studies, but shows at least a 95 percent chance that a doubling of carbon dioxide, which the world is on course to reach within the next five decades or so, would result in warming greater than 3.6 degrees Fahrenheit (2 degrees Celsius) relative to preindustrial temperatures. That is the threshold beyond which scientists say the Earth will suffer dangerous effects — disruptive sea level rise, intolerable heat waves and other extreme weather and permanent damage to ecosystems.
Staying below that is still possible. If steep emissions cuts are made in the near-term, a doubling of carbon dioxide levels could be avoided.
Earth's global “climate sensitivity” is a fundamental quantitative measure of the susceptibility of Earth's climate to human influence. A landmark report in 1979 concluded that it probably lies between 1.5‐4.5°C per doubling of atmospheric carbon dioxide, assuming that other influences on climate remain unchanged. In the 40 years since, it has appeared difficult to reduce this uncertainty range. In this report we thoroughly assess all lines of evidence including some new developments. We find that a large volume of consistent evidence now points to a more confident view of a climate sensitivity near the middle or upper part of this range. In particular, it now appears extremely unlikely that the climate sensitivity could be low enough to avoid substantial climate change (well in excess of 2°C warming) under a high‐emissions future scenario. We remain unable to rule out that the sensitivity could be above 4.5°C per doubling of carbon dioxide levels, although this is not likely. Continued research is needed to further reduce the uncertainty and we identify some of the more promising possibilities in this regard.
When this COVID-19 pandemic ends, a return to ‘normal’ would return us to a path leading to a global catastrophe. We need to choose a different path as we reopen the economy. A path that weens us off of fossil fuel consumption, and quickly.
We shouldn’t return to the path to our destruction.