Why does global warming mean global weirding? Why is everything supposed to get worse in a warmer world -- more droughts and more storms? Isn't anything supposed to get better?
Here's the bottom line:
CO2 is a greenhouse gas. Because of the actual physical size and shape of a molecule of CO2, it's just the right size to interact with energy of a certain wavelength -- infrared radiation, more commonly known as heat. When this infrared radiation (heat) encounters a molecule of CO2, the CO2 first absorbs the radiation (heat) and then puts it back out in all directions - it re-emits it.
Because there's CO2 all through our atmosphere and there are millions and millions of these little CO2 guys absorbing and re-emitting heat in every direction, the overall effect is for most of that heat to be kept within the atmosphere. Some does get put out into space, but most of it gets trapped inside our atmosphere, which means that heat sticks around, making our planet warm.
So, the more CO2 we've got in the atmosphere, the greater the chance that this heat that's coming off the Earth's surface will encounter a molecule (or lots of molecules) of CO2 on its way up (heat rises, right?) and eventually end up getting trapped inside the atmosphere.
More CO2 = more heat trapped!
Heat is just one form of energy. So having more heat in system means having more energy in the system. And energy is what's needed to DO STUFF. Like evaporate water or melt ice or warm up air or water. So, that's what it gets used for - doing all those things: evaporating more water and making a "typical" storm bigger. Or a "typical" drought drier. Or a "typical" heat wave hotter.
You could think of having all that extra energy available as sort of like having extra money lying around. You could stash it away in the bank to use later, but most people would probably want to spend it and put that money to work - a faster, flashier car, a bigger house, more fancy gadgets and appliances.
So just like you can go into a neighborhood with lots of big, fancy houses and you know that means there's a lot of money there, when you see a really big storm / wild fire / heat wave / drought, you know that means there's a lot more energy there than a smaller such event.
This is why global warming means global weirding. All this extra heat / energy gets used to wreak havoc on our climate system and therefore on all of us, too.
So... can any of this extra heat be a good thing? Like a superhero who decides to use his powers for good, not evil?
I looked through the latest IPCC report to find what it said about possible positive outcomes of climate change...
... there weren't a lot to be found, sadly, and those I did find were almost always couched with a caveat of a negative consequence that balanced out the positive. Here are a couple, though:
-A longer growing season in mid-high latitudes means an increase in crop productivity for some areas, including North America. However, this is only the case up to about 1-3ºC warming (2-5ºF). Above that, crop productivity is supposed to go back down. Boo...
-Commercial timber production is also expected to increase a little in the near-term, because of more CO2 for those trees to use, but it's expected to decrease in the long-term because it just gets too hot.
-"Climate change is projected to bring some benefits, such as fewer deaths from cold exposure. Overall it is expected that these benefits will be outweighed by the negative health effects of rising temperatures world-wide, especially in developing countries." (IPCC 2007)
A couple other benefits are reduced heating costs in cold parts of the world and the opening up of the fabled Northwest Passage over Canada. In both these cases, though, it's not hard to come up with the down-sides to these situations:
For every home that doesn't spend as much money on heating, there will be several more that will be spending more money (and energy) on cooling. And although opening up the Northwest Passage might be a great thing in terms of shipping, it brings with it a whole lot of other problems as well, as the almost uninhabited northern border of Canada gets developed. (This is where Baffin Island is, where I did my research for my Master's, so I can tell you that there really isn't a lot up there right now. It's desolate, isolated, untouched and incredibly beautiful!) (Read here for an interesting, but dated - 2005 - NY Times article on the opening of the Northwest Passage.)
So, sadly, any of the benefits of global warming look like they're going to be far outweighed by the negative impacts - especially in the long term. We ourselves might not have to face them, but our children and our grandchildren will.