Committed Warming

We’re already committed to one more degree (Celsius) of warming from the greenhouse gases we’ve already pumped into the atmosphere, according to an article in this week’s issue of Science. The article, by NCAR’s Tom Wigley, stresses the importance of the thermal inertia of the Earth’s oceans. On the other hand, if we continue to emit greenhouse gases at the same rate, we’re committed to 2-6 degrees Celsius of warming by the year 2400.

That’s a lot, no matter how you qualify it. Sea levels will rise approximately 10 cm/century if the atmosphere remains unchanged, and 25 cm/century if greenhouse gas emissions stay the same. In order to stabilize global mean temperatures, the paper concludes, we’ll have to reduce emissions of greenhouse gases to “well below present levels.”