Scientists at Boulder’s National Center for Atmospheric Researchare cautioning that the planet is closer to potentially catastrophic warming than is widely believed.
The year 2015 was the hottest on record, with the average annual temperature a full 1 degree Celsius (1.8 degrees Fahrenheit) warmer than in pre-Industrial times.
That is halfway to the cap of 2 degrees C (3.6 degrees F) that global leaders set in Paris in December to prevent potentially catastrophic warming.
However, NCAR senior scientist Gerald Meehl believes the Earth is effectively already well beyond the 1 degree C that the planet is confirmed to have already warmed.
Given the physics of Earth’s climate system, warming continues well after greenhouse gases are put into the atmosphere. That is because the oceans keep warming for decades in response to greenhouse gases that already have entered the atmosphere. That makes for a lag in the climate system.
Therefore, Meehl asserts that research shows the Earth is already assured about 0.5 degrees C of additional warming, even if levels of carbon dioxide in the atmosphere could be immediately stabilized.
That extra warming means that the planet is effectively three quarters of the way to the 2 degree C cap set at the 2015 United Nations Climate Change Conference, or COP 21, in Paris in December.
“We’re not there yet — we’re at about 1 C, but if we stabilized concentrations right now, we’re committed to about another 0.5 C warming,” Meehl said in an email.
Hitting the critical 2 degree C increase, and incurring the dire results to life on Earth that scientists forecast in association with that benchmark, is not a foregone conclusion, Meehl said.
“It’s still avoidable, but we have a very narrow window of opportunity (a couple of decades) and it’s closing fast,” Meehl said. “The longer we wait, the harder it will be to achieve that target.”
A reality that can’t be sidestepped
Meehl has been persistent in advancing this perspective on global warming. He was the lead author of a study in 2005, which quantified the relative rates of sea level rise and global temperature increase to which the planet was already committed to in the 21st century.
That study said that if atmospheric levels of greenhouse gases leveled off, globally averaged surface air temperatures would still rise about a half-degree Celsius (1 degree Fahrenheit) and that global sea levels would rise another 4 inches, from thermal expansion, alone by 2100.
He said his perspective of the dynamics at play has not changed since that study was published.
“Committed warming is a physical property of the system and something you can’t get around,” he said. “You have to take it into account in mitigation scenarios and if you are trying for the 2 C target, emissions have to be cut so that concentrations of GHGs (greenhouse gases) start coming down to offset the committed warming.
“So just stabilizing concentrations isn’t enough, the concentrations have to drop at some point to get to that warming target, and that’s as true now as it was in 2005.”
Meehl and other scientists have warned that the emissions cuts proposed during the Paris talks, while critical for lessening future climate change, may not be sufficient. They are studying a hypothetical scenario in which society later this century actually achieves “negative emissions” by pulling more carbon dioxide out of the atmosphere than is put into it. That would have the effect of cutting greenhouse gas concentrations and negating the committed warming.
To do so would entail massively scaling up existing technologies. Biological organisms, for example, could be deployed to soak up carbon dioxide. Or carbon dioxide from power plant emissions could be captured and stored underground.
‘We will blow right through a 1.5 C warming’
Meehl gets support in his remarks from colleague Kevin Trenberth, distinguished senior scientist at NCAR — but Trenberth said “it’s actually worse” than Meehl has said.
“The problem is that firstly there is a lot of inertia in the infrastructure and in the climate system, so that even if we, in the U.S., and globally, decided to act now to prevent 2 degree warming there is almost nothing we can do to stop it,” said Trenberth, adding that its onset can, however, be slowed.
“Coal-fired power stations have a planning lif time of over 40 years, so even with the EPA and administration’s Clean Power Plan, it takes 20 years to make a noticeable difference. And it takes 40 years for the climate system to respond, as the oceans are still responding to what has happened thus far,” Trenberth said.
The scientists’ remarks come the same week that the U.S. Supreme Court at least temporarily blocked the Obama administration’s implementation of new Environmental Protection Agency regulations calling for cutting emissions from electric power plants, with a stay ordered in response to a lawsuit from 29 states and a coalition of industry groups and corporations.
“Carbon dioxide levels will continue to climb for the foreseeable future,” Trenberth said, “and we will blow right through a 1.5 C warming by about 2030, and 2 degrees C warming by 2060 or so. We might be able to delay that till 2080. with big efforts.
“Mind you, these efforts make a huge difference further into the century.”
Charlie Brennan: 303-473-1350, brennanc@dailycamera.com or twitter.com/chasbrennan
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