24 October 2005

Global Warming

The topic of global warming is a hot one - har har! No seriously, every industrialized country thinks it's a big deal, except the US. Global warming is defined as a worldwide trend for warmer temperatures on average - it is also known as climate change, as it's important to distinguish that it is a large scale thing (as climates are), and not a small scale thing (as weather is). The term "climate change" is also less politically loaded here in the States than "global warming." There are a few important questions that must be answered to fully understand global warming.

  1. Is it happening?

  2. If so, what is causing it?

  3. Can human activity be causing it?

  4. Whether or not humans cause it, could we stop or reverse it?

  5. If we can, should we?

1. Is global warming happening?
YES. The only person who could possibly deny this part is the great Dubya himself. Well, and a few woo-hoos who also believe that the Apollo program was faked.

The actual evidence is very strong. We have direct thermometer measurements of the temperature since the mid-1800's, and the average temperature has increased by a full Celsius degree since then.

Global Temperatures 1855 - 2003

Prior to then we need to use indirect methods of calculating the temperature or climate. The most interesting (and least believable) one I've seen is a study of the backgrounds in historical paintings. During what was known as the Little Ice Age, paintings showed more clouds than they did before and after. Like I said, I'm skeptical of it. A better method is tree rings: the thickness of a tree ring indicates how good the growing season was for the tree, and this includes information such as the rainfall and temperature. That only goes back as far as the oldest tree we've cut down, so longer ago than that we need to measure ice core samples - the thickness of ice that's been laid down in glaciers over the last millenia. Graphs of these data show that prior to the 1800's the Earths' temperature was relatively flat. In other words, the temperature has jumped since the 1800's. Global warming IS happening.

2. What is causing global warming?
Probably a runaway greenhouse effect, or maybe increased input of energy (i.e. solar output).

In moderation, the greenhouse effect is a good thing. Without it, we'd be as cold and lifeless as Mars. In an actual greenhouse, light and heat from the sun pass in through the glass, but not all of it makes it back out through the glass. The excess light and heat reflect around inside the greenhouse and heat it up. Eventually the temperature does stabilize at a higher temperature than the outside air.

On the Earth, it's the atmosphere that keeps the heat and light in. You have witnessed this yourself - the easy one to visualize is how on clear winter nights it's colder than on cloudy winter nights. This is because the clouds help trap more heat than the clear air. Same reason why deserts are frigid at night. An everyday example though, is "Why is the sky blue?" Because of the light from the sun that gets scattered in all directions. The blue in the sun's light gets scattered more than the red, so the blue looks like it's coming from all over, while at sunset the blue goes away from the direction of the sun leaving it looking red.

What makes the process "runaway" is when too much heat and light gets trapped. Specifically, we know that chemicals such as carbon dioxide (CO2) are good greenhouse gasses. Like historical temperatures, we have historical records of carbon dioxide only for the past 50 years or so. Those show CO_2 increasing, which seems to confirm the hypothesis that it causes global warming. Another piece of evidence is, well, can you think of something important that happened in the mid-1800's? The industrial revolution and steam power (which releases CO_2). That led to cars (1910's) and even more CO_2. In fact, we can today measure how much CO_2 the world creates, and it matches reasonably well with how much we observe in the air. It is currently the leading theory of the cause of global warming.

However, if you've been reading this blog a while you know that scientists can never be 100% sure of anything. A competing hypothesis is that the sun has been getting brighter. If there's more light coming into the greenhouse, of course it'll get hotter. Again, we only have limited data, which so far is inconclusive, so it is unfalsifiable with current data.

3. Can human activity be causing it?
Yeah. Ditto above. There's evidence pointing that way, but it's "only" a theory.

I Drew This: Consensus

4. Whether or not humans cause it, could we stop or reverse it?
Yeah again. We know that CO_2 at the very least adds to the greenhouse effect and global warming, so if we reduce CO_2 emissions as per the Kyoto Protocol, we'd help to reduce global warming.

5. Regardless of whether humans caused global warming, if we can stop it, should we?
Probably. Regardless of whether a kid knocked out your window with a baseball or a tree fell on your house, should you replace the window? Probably.

If global warming's a Bad Thing, it doesn't matter where the blame lies, we need to fix it. And yeah, for the most part it IS a Bad Thing: we're losing whole islands in the South Pacific, whole glaciers and the ecosystems they support, and even the winter sports industry is being hurt. :-P

On the other hand, there's probably a few PETA members out there who say "if it's natural, it's not our place to interfere." While I can understand that point of view, I'm not sure I agree. If a killer asteroid were heading towards the Earth, I'd sure as heck wanna find a way to stop it and save us.


Peter said...

Good post Enviroman Says

Enviroman asks: "Have the frequency and ferocity of hurricanes increased due to global warming?"

Tor said...

Thanks for taking on this subject in an even-handed manner. Since exchanging blog posts with Dan Rhoads on this, I've been doing some reading. Just finished Earth's Future Climate, by Henry Willis. Do you have any other good resources for lay readers who can slog through a moderate amount of jargon?



zandperl said...

Tor: I'm afraid I do not. I would say start with the Wikipedia global warming article and browse through the links at the bottom of the page - they even specify if it's a skeptical page and such.

As for my "evenhandedness," thank you, but I'm sure many conservatives and industrialists would disagree and say that I am liberal-biased. I readily admit it's really hard to be unbiased, but I try. I will not present irrational viewpoints, but I will point out failings in and alternatives to the theories I believe. I'll also point out those alternatives' weaknesses. :-P

The Diaper Dame said...

Thanks for researching these topics and posting the information for those of us who are too busy to go hunting around the Internet to find it for ourselves, but who want to be kept up to date on what's happening just the same. I'll be coming back for more.


island said...

The only part that I don't buy is that global warming necessarily bad, since Milankovitch models predict that global warming is offsetting a short, then long-term cumulative trend toward glaciation.

I don't believe that we can fool mother nature, because I don't believe that we can exist *above* the ecobalance that we are contributing members of.

How arrogant... who are we to think that we can "break (nature's) windows"?... That reminds me of religious pride, except that it's the kind that "free-thinkers" embrace... praise the almighty... "Uncertainty Principle".

I do believe that the most accurate cosmological principle, is biocentric in nature... so that would explain my postion... ;)

... as supported by the physics

zandperl said...

The only part that I don't buy is that global warming necessarily bad, since Milankovitch models predict that global warming is offsetting a short, then long-term cumulative trend toward glaciation.

That's a good point. The greenhouse effect is definitely a GOOD thing in moderation, as it's preventing us from being cold like Mars. However, too much greenhouse effect and too much global warming is definitely a BAD thing, as we would end up hot like Venus - it's so hot on the surface of Venus that lead would melt, and the few space ships we've had land on the surface only lasted a few minutes at most. Comparing the Earth's greenhouse effect (and incoming sunlight) to that of Mars and Venus is often called the Goldilocks Problem.

However, I would say that for Earth, look at the numbers, and look at the definition of Global Warming. The numbers say the worldwide temperature is increasing - if we wanted to balance out the natural tendancy for ice ages, we should have a steady temperature. The phrase "global warming" implies the same thing - the temperature is increasing, not staying the same.

Perhaps after a few hundred more years it will taper off, but we don't know yet where the temperature will stop, and whether it'll be low enough that most species can survive, or high enough that even humans will have a hard time.

island said...

I'm still not convinced, because glaciation occurs by way of a much more severe cumulative runaway effect that can only be offset by an equally drastic counterbalancing tendency.

It only makes sense that accelerated warming is the natural mechanism that will (hopefully) save us, given the comparitively short amount of time, considering that humans exist at the tail end of a 10,000 year long interglacial that is racing into a 100,000 year long ice age. Like squirrils that innately bury nuts for the winter... humans innately warm the climate for the same reason.

I don't think that scientists have any right to make any categoric statements about what should be done without some very hard proof that Milankovitch is wrong.

Don't be so bloody fanatically sure about it... in other words.

Which brings me back to the anthropic principle... the balance between the diametrically opposing runaway tendencies of big business vs. the stagnation promoting "green movement" defines yet another anthopic coincidence... like the universe is "near"-perfectly balanced between runaway expansion and gravitational recollapse... the flatness of the universe defines a grand scale **Ecobalance**... just like all of the other anthropic coincidences.

Don't be so arrogant.

zandperl said...

I'm still not convinced, because glaciation occurs by way of a much more severe cumulative runaway effect that can only be offset by an equally drastic counterbalancing tendency.

Here's an analogy that perhaps explains my viewpoint. If I make a lot of money, that means I can afford to spend a lot of money on renting a huge apartment. But if in the end my expenses are greater than my income, it's not good.

Making a lot of money is like the Earth having a strong tendancy towards ice ages as Milankovitch says. Spending a lot of money is like global warming. Just like you don't want your spending to be greater than your income, you don't want the global warming to be greater than the ice age.

A better analogy would be in cooking a frozen chicken. Let's say you take the chicken out of the oven and find that it's burnt on the outside and frozen on the inside. You can safely conclude that the oven was put on too high a temperature for too short a time and you weren't able to thaw the inside while the outside was too hot. You can see right there from the results that you needed a more subtle heat to thaw the frozen chicken.