Antinuclear

By Justine Calma@justcalma  Jul 7, 2020,  It could take decades before cuts to greenhouse gases actually affect global temperatures, according to a new study. 2035 is probably the earliest that scientists could see a statistically significant change in temperature — and that’s only if humans take dramatic action to combat climate change.

“I foresee this kind of train wreck coming where we make all this effort, and we have nothing to show for it,” says lead author of the study, Bjørn Samset. “This will take time.”

It will be time well spent if we manage to cut emissions — even if we have to wait to see results. Humans have so far warmed up the planet by about 1 degree Celsius. That’s already come with more devastating superstorms and wildfires and has forced people from Louisiana to Papua New Guinea to abandon their homes as rising sea levels flood their lands. Even keeping the planet to the 2 degree goal would result in the near annihilation of the world’s coral reefs. Taking into consideration all of the commitments from world leaders to work together on climate change, we’re currently careening toward global warming of about 3 degrees Celsius above preindustrial levels.

To avoid burnout and keep aspirations high when it comes to tackling climate change, scientists and policymakers will need to be realistic about what’s ahead. The first line of the new study, published today in the journal Nature Communications, reads: “This paper is about managing our expectations.”

The study looks at the effects of cutting down on carbon dioxide, black carbon, and methane emissions. Carbon dioxide is the toughest greenhouse gas to tackle because so much of the world economy still relies on burning fossil fuels.

Methane (a more potent greenhouse that comes from agriculture and natural gas production) and black carbon (a big component of soot) are, in theory, easier to cut back. Using climate models and statistical analysis, Samset and his colleagues wanted to know whether addressing these other pollutants might lead to faster results. Their analysis isolated the effects that reducing methane and black carbon might have. They found that temperatures might respond quicker to axing these pollutants, but it wouldn’t have as big of an effect in the long term as pushing down our carbon emissions. The best bet is to tackle all three at once.

“We kind of break this apart and try to see, is there a shortcut? Is there anything we can do to give people the impression that things are having an effect? And unfortunately, the answer is no,” says Samset. “There’s no quick fix to this.”

Part of the problem is that carbon dioxide can persist in the atmosphere for hundreds of years after being released by burning coal, oil, and gas. Natural variations in climate can also delay the impact that cutting down greenhouse gases has on global temperatures.

“There is this fundamental misunderstanding of the climate system by non climate scientists trying to use trends on a 10 year time scale for climate change, when [with] climate change a 100 or 200-year timescale is relevant,” explains Natalie Mahowald, a climate scientist at Cornell University who was not involved in the study.

“All our hard work today, we will not be able to see for 20 or 30 years — this is the crux of the problem,” Mahowald says. “Humans have a really hard time doing something for future generations.”