New Climate Study Says We’re All Gonna Fry

A new study, "An assessment of Earth's climate sensitivity using multiple lines of evidence," has determined that we will probably end up with a global average temperature rise of between 2.6 and 3.9 degrees Celsius. Optimists might say "hey, that's not so bad, for 40 years scientists had a worst-case scenario of 4.5 degrees Celsius!" 

The pessimists will point out that in 2015 the signatories to the Paris accord agreed to reduce emissions enough to hold the global rise in temperature to 2 C. In 2018 the IPCC said hold on, that's too much, we have to hold the temperature rise to 1.5 C to prevent catastrophic changes. At the time, Kendra Pierre-Louis of the New York Times tweeted that "Based on their description the difference between 1.5 °C and 2 °C is basically the difference between The Hunger Games and Mad Max.”

In the summary, the authors write "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."

The researchers do not rule out a higher temperature rise; "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."

The study follows many scenarios to try and narrow the range of climate sensitivity. Andrew Freedman and Chris Mooney of The Washington Post explain:

To produce the study, the group of researchers worked like detectives, breaking up into teams that sifted through multiple sources of evidence. Some of the data examined include instrument records since the industrial revolution, paleoclimate records from coral reefs and ice cores that provide evidence of prehistoric temperatures, and satellite observations and intricate models of how the climate system works. To reach their new, authoritative estimates, the researchers required that multiple lines of evidence point to the same general conclusion and that this be explained without being the result of a bias that influences one or more sources of evidence.

This is all based on the assumption that CO2 in the atmosphere, currently at 415 PPM, will continue to rise to about double of pre-industrial levels of 280 PPM, or 560 PPM. Stopping that rise and preventing that doubling can reduce the heating. As study co-author Gavin Schmitt tells the Post, "The primary determinant of future climate is human actions." 

Study contributor Kate Marvel of the Goddard Institute was interviewed for Bloomberg and reiterated:

The number one determinant in how hot it's going to get is what people are going to do. If we gleefully burn all the fossil fuels in the ground, it's going to get very hot. If we get extremely serious about mitigating climate change—cutting our emissions, moving off fossil fuels, changing a lot about our way of life—that will have a different impact on the climate.

As someone who has been trying to live a 1.5-degree lifestyle, I joked that I might as well go buy a Ford Bronco, drive 50 miles and order a big steak, because according to this study, we will not even be close and it's all hopeless. But it's not; these scenarios are all based on doubling of CO2 in the atmosphere and we don't have to go there.

In the end, the study just emphasizes the point: We all have to double down on reducing CO2 emissions and do it now. As Marvel tells Bloomberg, "There’s a tendency to try to put the perfect numbers on things, to say we have 12 years to save the planet. Honestly, we have, like, negative 30 years to save the planet."