Armour pointed to a pair of feedbacks that have yet to take effect, but are likely to lead to significant levels of warming.
“Over the next several decades to centuries we expect the Southern Ocean to warm up almost as much as the Arctic and get that big, positive feedback to start kicking in,” he said. “So it’s really that delay in the positive feedbacks kicking in that causes this increase in climate sensitivity into the future.”
That feedback in the southern hemisphere is projected to occur when ocean temperatures in the Southern Ocean warm, melting sea ice, like is already happening in the Arctic, causing the ocean to absorb more sunlight and leading to greater amounts warming.
Increased warming in the eastern tropical Pacific over the next several decades, he added, is is likely to diminish cloud cover in the region. That cloud cover, like sea ice in the Arctic and Southern Ocean, reflects incoming sunlight.
“Initially in the very early stages of global warming, like today, like we’ve seen over the last hundred years, your clouds in the eastern tropical Pacific are actually acting to limit global warming, it has a negative, damping impact,” he said. “But in the future, say over the next several decades, we expect those to be a positive feedback, enhancing global warming.”
What Armour didn’t find was any suggestion that Earth’s climate might somehow absorb all of our increased greenhouse gas emissions and warm less than any climate model has predicted.
“There are no examples of models showing a decrease in sensitivity by any significant amount,” he said. “That range of predicted warming in the future, is actually, as far as we can tell, pretty accurate.”
And those predictions, whether gleaned from UN reports or NASA or any other peer-reviewed account, warn of dangerous changes to the climate, which could imperil millions of people and future generations.
“This is a good result for the scientists — because it closes a hole of inconsistency — but in terms of the ‘public’ argument, this won’t matter,” said NASA’s Schmidt. “The contrarians have been ignoring studies like this for years, and I doubt they will stop doing so now.”