by positive feedback from the earth's climate system
A new paper shows that over the last 400,000 years, small amounts of global warming produced by variations in the earth's orbit around the sun have triggered much greater amounts of global warming due to various positive feedback effects in the earth's climate system. In the past the earth has quickly shifted from cold ice ages to warm interglacial ages following very small shifts in the amount of solar radiation reaching the earth.
This research suggests the earth's climate is extremely sensitive ---- when something happens that gives the earth a push either toward warming or cooling, other things like cloud cover, humidity, snow cover, glacier extent, desert extent, ecosystem changes, etc. quickly respond to the initial climate forcing, and then combine to push the climate even farther in that direction.
The climate feedback effects don't happen instantaneously. In the paleoclimate record there is a lag of decades to centuries between the initial nudge to the climate and the much larger response from the climate system.
The implications of this pattern of nudges to the earth's ciimate followed by much larger feedback effects that push the climate farther in the same direction have obvious implications for modern human-caused global climate change. Humans have nudged the climate system by adding more greenhouse gases like CO2 to the atmosphere over the last 150 years, increasing atmospheric CO2 from ca. 280 to 400 ppm. We've already seen global warming of about 1°C for the planet---but feedback effects are just beginning to kick in and act to increase the magnitude of global warming. And continued use of fossil fuels is inexorably raising the level of CO2 in the atmosphere towards levels of ca. 1000 ppm by the year 2100.
We know increasing CO2 causes global warming. We know global warming causes more global warming. I'm very curious to see exactly how much additional warming will be created over the next few decades by the various climate feedback processes operating on the earth.
No comments:
Post a Comment