What is the temperature supposed to be?

Question

This one's for the Global Warming gang. The Earth may be in a slight warming trend, I'll give you that. My question is, how do we know this is not normal? Earth has been a constantly changing planet for millions of years. Do we really expect it to stop changing just because we're here? How do you know for a fact that the temperature isn't supposed to be warmer in 5 years than it is now? You can throw averages around all you want, that really doesn't mean anything if you can't explain why you think the Earth is supposed to stay a certain temp. for the rest of time.

Answer 1

Trevor, from whom did you get the ridiculous assertion that the current warming is time times faster than any time in the last 10,000 years? Nothing could be further from the truth. In fact temperature reconstructions from ice core data in both antarctica and greenland show just the oppposite.

According to the latest IPCC report, the earth warmed by 0.6*C over the last century. This is hardly a very fast rate. In fact the IPCC shows that there was 0.5*C of warming between 1910 and 1940, about 0.3*C of cooling from 1940 to around 1970, and then more warming from 1970 to present.

The ice core data (see attached link) shows antarctic warming of about 2.7*C in 200 years starting about 800 years ago, followed by 3*C of cooling in 200 years starting about 600 years ago, followed by 2.2*C in one century starting about 400 years ago. This temperatures swings are far greater (both warming and cooling) than what has been observed in the last century. The study also shows that greenland temperatures have been 1-2 degrees C warmer than present for most of the last 10000 years.

Stop spewing nonsense about the earth is warming faster now than anytime in the past. It is simply not true

Answer 2

The earth has been around a long, long time - about 4.567 billion years. We don't know much about what happened for the first 4 billion years but we have a pretty accurate picture stretching back 542 million years. In that time the earth has either been warming or cooling, there have been 4 complete ice age cycles including times when the world has been much warmer than it is now and there's be no ice caps at all. In fact, where the ice caps are now were afforested at one time.

There are certainly natural cycles but they occur over very long periods of time - thousands and millions of years. From time to time the earth goes 'crazy' and there are periods of very rapid warming and cooling. The most recent one started 18,000 years ago when the earth began warming and the glaciers started retreating. This lasted for 7,500 years by which time the glaciers had retreated and the world was 8°C warmer, in the next 10,000 years there was a further rise of 1°C.

When the world was in it's 'crazy' phase it was warming by about 1°C every 1000 years.

In the last 100 years the world has warmed by just over 1°C, ten times as fast as when the world was rapidly warming, 100 times as fast as the preceding 10,000 years. More recently temperatures have been rising even faster, about 0.5°C in the last 25 years.

In short, what we're seeing are temperatures rising many times faster than has ever before been known and the rate of change is continually accelerating.

This isn't surprising. We know what causes the earth to warm and cool and the dynamics of global warming are well understood (it was in 1896 that they were first explained so we've now got 111 years of research and experience). If there's an increase in greenhouse gas levels there has to be a corresponding increase in temperature and this is what we're seeing now.

Since humans first set foot on the planet levels of atmospheric CO2 have varied between 190 and 310 parts per million by volume (ppmv). From year to year levels have hardly changed at all but in the last 50 years there's been an increase of 75 ppmv - this corresponds with the amount of CO2 emissions we've produced. Current levels are 385 ppmv, significantly more than has ever before been known and rising at an unprecedented rate.

In short, there's a perfect correlation between industrial activity, CO2 and other greenhouse gas levels, global warming and climate change. It would be very remiss if humans were unwilling to accept the consequences of our actions.

No-one is saying that the temp of Earth should remain constant, it would be foolish for anyone to suggest this. We know temperatures change naturally and always have done, we also know that we're in a natural warming trend. However, it's the extremely rapid changes in temperatures that are causing concern, they're incomparable to anything seen in 542 million years of climate history.

No one can say for certain how much temperatures would have risen if we hadn't intervened because there's so many complicated factors to take into account. But even assigning a maximum value to all natural variations produces a rise far below that which we're experiencing.