This has been known for years. It is very frustrating to see people ask questions like "well, what we don't know is what will global warming do?" Global warming has done, already, quite a bit and it is insulting to our collective intelligence and an affront to the families of those who have died from it to pretend nothing has happened. From desertification in Africa to heat waves in Chicago, global warming has killed people. Perhaps the following video from PBS will make this a bit more palpable to those who can't grasp this concept.
I have not yet watched the video, but I remember in 2003 some 6000 elderly people died in an unprecedented heatwave in Europe (Wiki puts the total heat deaths at over 18,000). I thought at the time - "Wow if that had been terrorists it would have had a massive response, but since it is global warming it will scarcely raise an eyebrow." And that is how it has been. Our reaction to various threats is very emotional, not very rational and may not serve us well/
Don't worry, if Romney wins, he'll scrap the PBS and then we won't have any more scary videos to upset us.
@salor: That heatwave was not directly caused by global warming. Exceptional weather happens all the time. Comparing AGW wth terrorists is exactly the kind if emotional response you apparently take issue with.
@greg: The increase in temperature in the cities is mostly caused by urban development (more built-up areas, higher buildings). Big, sprawling cities are recent phenomena, and even without AGW (which, for the record, I do not question), cities like Chicago would have to re-evaluate how they deal with weather features.
The desertification of Africa has been going on since we came out of the last ice age. The growth of cities is more to blame for the increase in average temperature than GW.
Taking action against AGW is important and urgent, but let's not overplay our hand.
Bill, the baseline for temperature has gone up, so heatwaves are worse, and warm periods have become heat waves. That is what the scince says. So, you've got that wrong.
Yes, there is an urban heat island effect that makes this worse in cities. That is part of the point of this video. You should watch it. Without global warming, cities would not have as severe an effect.
The desertification of Africa, that term, refers to a shift from savanna/grasslands to arid in various regions over the last few decades.
A major study funded by the Koch group (big oil) carried out by scientists who were global warming skeptics looked at the heat island effect. The found the heat island effect to not affect the conclusion that anthropogenic global warming is real. They stopped being skeptics. Science marches on.
Nobody is overplaying anyone's hand, Bill.