There have been a lot of articles posted recently saying that the original Intergovernmental Panel on Climate Change (IPCC) reports that said we could expect a global average temperature rise of 5 degrees C were wrong. They were wrong because they were too conservative. What were not understood when the first report was written were the feedback loops associated with increasing temperatures. Some examples of feedback loops where there was not enough data available were melting permafrost, ocean evaporation and cloud cover, as well as glaciers melting.
Melting glaciers are typically noted for their impact on rising sea levels. What isn’t frequently stated is their reflectivity, or the fact that white reflects much more light than dark colors. As anyone with a dark colored car knows from parking in the sun, the more sunlight absorbed, the warmer the environment. When glaciers melt, they expose land or water, which are both darker in comparison. As the Arctic and Antarctic get warmer, more ice melts, removing the planet’s natural cooling mechanisms, in turn making it warmer.
In addition to the lost reflectivity, melting glaciers over land also expose and melt permafrost. Melting permafrost releases methane, which is an even more potent greenhouse gas than carbon dioxide. Again, as these regions get warmer, they release gases that make the planet even warmer. Fortunately, there are some effects that work in the other direction, like cloud cover.
As oceans get warmer, more water evaporates. As evaporation increases, cloud cover increases, and clouds also reflect light back into space. When the original 5 degree C warming estimates were released, these effects were known, but the extent they came into play was not. Estimates now say that continuing on our current path of emissions will lead to a global average temperature increase of up to 9 degrees C.
