The general view of the Paris agreement reached last week among climate scientists seems to be that while it won't halt global warming, it is an important step in that direction.
On a more micro level, however, their opinions run the gamut and reveal both high praise and harsh condemnation of the global accord.
James Hansen of the Earth Institute at Columbia University, and former director of NASA's Goddard Institute for Space Studies, says the agreement is "just worthless words" and a "fraud."
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Meanwhile, the director of the Earth Institute, Jeffrey Sachs, terms the agreement "historic" and "a diplomatic triumph."
Their Earth Institute colleague, Gavin Schmidt, says the agreement is "not the greatest thing in the world, but it is a necessary first start, and we're in a better position this week that we were two weeks ago."
Schmidt is Hansen's successor at NASA.
Paraphrasing Winston Churchill's famous quote that democracy isn't perfect and "the worst form of government except all those other forms that have been tried," Schmidt tells CBC News, "this treaty is probably the worst of all possible treaties, except the others."
He also points to past global environmental issues, such as acid rain, ozone depletion and sulfur pollution, whose solutions were also implemented incrementally, "with initial pledges that don't match the scale of the problem, but people find out that it's actually easier to do these things than they first feared."
Pledges insufficient to meet target
CBC News spoke to three climate scientists, and all agreed the country pledges made during the Paris talks are not sufficient to meet the stated goal of limiting the rise in global temperatures to 2 C. Still, all three view the agreement positively.
Nigel Arnell of the University of Reading in the U.K., who was in Paris for the talks, stressed the importance of simply getting an agreement, with nearly all countries signed up to it.
"The fact that we got an agreement with a temperature target, with a commitment to a direction of travel, with a commitment to improving and enhancing the financing that's going to be necessary to meet that direction, I'm pretty optimistic about it," said Arnell, who authored A Short Guide to Climate Change Risk, published this year.
Canadian climatologist Gordon McBean, the president of the International Council for Science, told CBC News there's a generally positive feeling about the Paris agreement in the scientific community. Governments are now taking climate change seriously and the idea of limiting warming to 2 C and moving toward 1.5 C in the future are excellent developments, he said from San Francisco, where he was attending the annual fall meeting of the American Geophysical Union.
However, McBean says it's "largely not possible" that the world will meet the 2 C target.
The planet has already warmed about one degree from the pre-industrial levels of 1850. He expects global temperatures will have risen by 1.5 C by mid-century, as they have risen about 0.2 C per decade over the past 20 years or so.
Global temperatures "will change at that rate through to 2050 regardless of emissions reductions, because of the lag time of our climate system," McBean said.
The goal of the Paris agreement — or COP21, for the 21st Conference of the Parties — was really to "prevent climate change over the last half of this century and beyond," he said.
He stresses that, "we have to take action now." That means Canada needs to move away from the oilsands, "leave some oil and, particularly, coal in the ground" and implement a carbon tax, he said.
"We need to look to a new sustainable type of economy that is not fossil-fuel dependent."
Commitments to be revisited, made more ambitious
NASA's Schmidt also expects the planet is on course to warm more than 1.5 C and that keeping warming to two degrees, while physically possible, will be extremely challenging.
The long-standing but somewhat arbitrary two-degree target isn't the key to assessing whether or not climate change is manageable, he notes.
Even now, after one degree of warming, the planet is feeling the impact of climate change, and "we'll see even more impacts, and whether those are dangerous depends very much on how close your house is to sea level."
Island nations, the ones most threatened by climate change, pushed to include the 1.5-degree target in the Paris agreement.
The agreement asks the Intergovernmental Panel on Climate Change to "provide a special report in 2018 on the impacts of global warming of 1.5° C."
While the pledges aren't commensurate with the problem, they cover only the next few years or decades, and the agreement requires them to be continuously revisited and for countries to adopt more ambitious targets every five years.
For Schmidt, a big plus of the accord is that governments now recognize the reality of climate change and the need for action. The direction we're heading in is now agreed, says Schmidt, so now, the focus should be, how to get there.
"Things will get easier, and people's ambitions will increase," he said.
Most of the developed countries have pledged to reduce emissions, but some countries, notably China and India, expressed their pledges as relative to GDP (China — the world's No. 1 greenhouse-gas emitter — does commit to capping its emissions, although when and at what level isn't stated). So, it's still a question of whether global emissions will go down.
"It's not clear what will happen if all the pledges are met because it depends on what happens after 2030," Arnell said.
"That's why the review bit in the agreement is really important."
For Arnell, now that the deal is out, "the question is, are we actually going to be able to deliver it?"
He says that, scientifically, it would have been nice to have a carbon budget setting limits on who can emit how much, but that was politically unrealistic. Instead, under the new accord, commitments are determined by individual countries.
"Each country is saying what it wants to do and then, in a sense, competing with each other to do the right thing," Arnell said.
Still, the agreement has no enforcement mechanism and no guarantees it will get implemented. So, now that governments are finally heeding the long-standing warnings about warming from climate scientists, it's up to the public to ensure they keep their pledges — and extend them.
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