New Orleans and global warming

Tomorrow (Sat 19 Jan) I leave Santiago to go back to the US for a week to attend the American Meteorology Society's annual meeting in New Orleans. I am not taking my laptop and am looking forward to a relatively technology-free week.

On a unrelated note, I was recently asked what my take was on global warming. I defer to the official World Meteorological Organization position, which I think explains things very clearly, in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). The IPCC is made up of over 1,000 scientists from most of the countries on the planet, and they have been studying climate change now for over two decades (some for much longer than that). Every four to five years, they gather to summarize the scientific research to that point, and in 2007 they had a series of meetings to compose the Fourth Assessment (the first assessment was released in the mid 1980s).

Basically the figures are a combination of observations and computer models to examine "How much have we warmed to-date" (and "Why?"), and "will we warm in the future?" The short answers are:

- warming has occurred globally since at least 1850, particularly in the polar regions.

- we cannot explain the levels of warming, using computer models, without incorporating man-made levels of greenhouse gases (CO2, methane, etc.) (I.e., the computers cannot reproduce our current temp levels using only natural variability).

- the next 100 years should see more warming (even at an accelerated pace), with different regions (continents, states, islands, etc) experiencing different levels of warming. Coincident with the warming is also the threat of prolonged droughts / floods (i.e., an increased occurrence of extreme events).

- yes, both the computer models and the data used to verify them have errors and uncertainty. but the "signal to noise ratio" of the cumulative uncertainty is large enough to confidently ascertain the trends (see figure 2).