Well, climate is essentially long-term weather. We don't have a fantastic definition of climate, but things like average rainfall, the range of rainfall, average temperatures, the range of temperatures, when the peaks are reached, etc. all play a role. There is a certain amount of randomness to it, but typically within a given range.
Individual weather events can exceed the normal range without being indicative of climate change. You can see tempestites in normally tranquil sediments throughout geologic time, for example. These events tend to be rare, however; therefore increased frequency can be indicative of climate change. It's kind of like a glacier. No single snowfall produces a glacier; it takes accumulated snows for years to do so. Similarly, no single weather event constitutes climate; but, taken as a whole, year after year, they add up to the climate of the region.
Climate is complex, however. There are multiple oceanic circulation systems, as well as atmospheric circulation systems, that all interact. Warmer temperatures in one area can be causally linked to cooler temperatures in another, due to these interactions. So yes, it's possible for even global warming to cause localized cooling, via several mechanisms. For example, shifts in thermohaline circulation can push warm-water currents further from an area, cooling it. If the Gulf Stream shifted to the other side of Greenland, England would rapidly become significantly cooler while eastern Canada would warm up considerably.Wind patterns can shift, causing some areas to increase in aridity while others become more wet. Shifts in sea levels also play a part--oceans function as enormous heat sinks. Take a drive in the summer from Long Beach to Bakersfield and you can see this in action. Higher sea levels inundate large areas, bringing that heat-sink further inland. This can cool some areas, by preventing the wild temperature swings they would otherwise encounter.
Add in such things as threshold events and forcing mechanisms over thousands of years, and it becomes possible for increased temperature to trigger an ice age.
The climate is changing. I'm not interested in why, particularly; the simple fact is that climate changes constantly (but not consistently). The real question in my mind is what to do about it. Personally I hope we are at the end of the ice age we're currently in, rather than merely in yet another interglacial; glacial periods are fairly horrifying in terms of civilization. Last time the ice sheets started in the Hudson Bay and extended down to central Ohio--meaning that Canada would basically be wiped out, and many of the cities in New England would be piles of rubble sitting in Pennsylvania. Not quickly--we'd have generations to prepare--but inevitably. The planet isn't normally in glacial periods (Zachos et al., 2001; Figure 2 is the money shot), and return to normal conditions would be a good thing. The issue is, it would EVENTUALLY be a good thing; the ecosystem would EVENTUALLY stabilize. The loss of human life could be catastrophic if we're not careful.
For further reading, I recommend Peter Ward's book "Futur Evolution". It discusses these issues, and more, in detail, as well as potential solutions.
Individual weather events can exceed the normal range without being indicative of climate change. You can see tempestites in normally tranquil sediments throughout geologic time, for example. These events tend to be rare, however; therefore increased frequency can be indicative of climate change. It's kind of like a glacier. No single snowfall produces a glacier; it takes accumulated snows for years to do so. Similarly, no single weather event constitutes climate; but, taken as a whole, year after year, they add up to the climate of the region.
Climate is complex, however. There are multiple oceanic circulation systems, as well as atmospheric circulation systems, that all interact. Warmer temperatures in one area can be causally linked to cooler temperatures in another, due to these interactions. So yes, it's possible for even global warming to cause localized cooling, via several mechanisms. For example, shifts in thermohaline circulation can push warm-water currents further from an area, cooling it. If the Gulf Stream shifted to the other side of Greenland, England would rapidly become significantly cooler while eastern Canada would warm up considerably.Wind patterns can shift, causing some areas to increase in aridity while others become more wet. Shifts in sea levels also play a part--oceans function as enormous heat sinks. Take a drive in the summer from Long Beach to Bakersfield and you can see this in action. Higher sea levels inundate large areas, bringing that heat-sink further inland. This can cool some areas, by preventing the wild temperature swings they would otherwise encounter.
Add in such things as threshold events and forcing mechanisms over thousands of years, and it becomes possible for increased temperature to trigger an ice age.
The climate is changing. I'm not interested in why, particularly; the simple fact is that climate changes constantly (but not consistently). The real question in my mind is what to do about it. Personally I hope we are at the end of the ice age we're currently in, rather than merely in yet another interglacial; glacial periods are fairly horrifying in terms of civilization. Last time the ice sheets started in the Hudson Bay and extended down to central Ohio--meaning that Canada would basically be wiped out, and many of the cities in New England would be piles of rubble sitting in Pennsylvania. Not quickly--we'd have generations to prepare--but inevitably. The planet isn't normally in glacial periods (Zachos et al., 2001; Figure 2 is the money shot), and return to normal conditions would be a good thing. The issue is, it would EVENTUALLY be a good thing; the ecosystem would EVENTUALLY stabilize. The loss of human life could be catastrophic if we're not careful.
For further reading, I recommend Peter Ward's book "Futur Evolution". It discusses these issues, and more, in detail, as well as potential solutions.
