I'll start by pointing out that the temperature data I've seen show that the planet appears to be at the END of the warm trend in its 250-thousand-year cycle, not the beginning.
With that out of the way: while global warming is a possibility, I don't think the evidence on the subject is anywhere near conclusive. The fact that the people right here in this thread (who are above average intelligence to begin with) are so bitterly divided about it demonstrates that pretty clearly.
My biggest caveat about the subject is that the one-degree spike we saw in the last century, while definite, is no different from any of the other spikes that have occurred naturally throughout the planet's history.
Second, we're trying to measure the amount of heat energy in a PLANET. A gigantic system with a whole lot of widely varying interacting systems. Land, water, air, living things, weather--all process heat differently. Clouds have a warming effect (water vapor is a greenhouse gas) and a cooling effect (reflection of radiation back into space). Water stores heat a lot more efficiently than the land does (meaning that water warms up by a smaller amount when it absorbs the same amount of heat), so you have to consider where all the heat is going. One of the web sites I browsed while examining the subject had a pair of graphs showing temperature in the troposphere and stratosphere over a couple hundred years--these two adjacent layers in the atmosphere had NO relation to each other on the graphs! Warm trends in the troposphere did NOT have matching trends in the stratosphere. Cleary there was a problem there--what kind, I don't know. Could have been that people were simply measuring wrong.
Third, the subject has been completely subsumed by political bickering. Anybody who voices doubt about the subject is immediately accused of lying, taking dollars from Evil Corporations, just plain being an idiot, or whatever else. There's a great deal of pressure on scientists to produce the "correct" findings. In that kind of environment, science is no longer science--it's peer pressure.
Fourth, it's known that temperature changes in BOTH directions can produce varying forms of environmental disaster--because it's happened lots of times. We've seen it in past Ice Ages; the amount of habitable land on the planet was lower, obviously (the rest being buried under gigantic sheets of ice), and of the land that was habitable, a larger percentage of it was desert or tundra. The amount of usable farmland was much smaller. TruePurple made a couple mentions of insects becoming more active; what he left out was that ALL life becomes more active as it gets warmer. Plants included. That means a larger food supply for all other animals as well as insects.
I have no objection to reducing greenhouse gases--but doing so at the expense of human welfare is a bad idea. Many of the planet's wars get fought over that sort of thing.
increase - this appears to bare no relation to such 'natural' changes as induced by solar activity, etc - unless, of course, the 'naturalists' are arguing another 'dinosaur killer'...
