Why do we compare the temperature now to the temperature 100 years ago to determine man's contribution to GW?

Question

Why do we not ask:
1) “How hot did it get before man-made global warming?”
2) “How much hotter is it now?”
This would give a more true indication of man’s contribution, would it not?

Answer 1

We actually don't. We look at the entire 120 years or so of instrumental temperature records, and see what the causes are. They change over time.

Before 1950 or so, it was mostly natural causes with a major contribution from greenhouse gases. From 1950-1970 greenhouse gases began to take over, but the effect was masked by simultaneous particulate (aerosol) air pollution. After 1970 the increase in greenhouse gases became overwhelming.

The clarity of the data with regard to the last point is so strong that it's the reason all but a very few skeptics understand the present cause. In statistical terms the "signal" from man made greenhouse gases is overwhelming. Even skeptics like Richard Lindzen, Bjorn Lomberg, and now, President Bush, understand and accept that Man is mostly the cause now.

Here's the picture:

http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution.png

Yes it was hotter many thousands of years ago. And coastlines and plant life were very different. Our modern society with massive coastal development and intensive agriculture wouldn't like that much.

Good website for more info:

http://profend.com/global-warming/

Answer 2

The problem is that there are too many variables. Human contribution would be nearly impossible to determine. What affect did humans have in getting out of the last ice age?

The world climate doesn't care about inconveniences to humans. People that build below sea level should expect bad things to happen eventually.

Answer 3

I've seen it supported by arguments using data from various timelines. I think the idea that only the last 100 years is being used to support it is in the category of a myth. There's always a hidden trap to these types of questions, in that responding at all contributes to the misconception that there's some kind of debate going on within science. That after all, is the biggest hoax of all.

Answer 4

Good temperature records go back 100 years. If you go back more than 100 years there are not good temperature records. And Man made CO2 releases 100 years ago were MUCH lower than what they are today. Cars and electricity had just been invented and were not yet in widespread use.

Answer 5

You're question soesn't make much sense--since scientists did just that long ago. They've tracked changes in global temperature back ovr 200 years with some degree of precision (beyond that there's a lot of data, but not as precise).

Signifigant global warming started about 100 years ago. But--that is not what tellus us that man is causing global warming--only that it s occuring. The evidence that our current global warming is caused mostly by humans is conclusive--but it depends on analysis o fHOW the global warming occurs, not simply that it is happening.

Answer 6

100 years ago automobiles hardly existed. And only about 1 billion people were polluting.Lots of horses were polluting too.By the way things are going on earth now scares me.Will our planet support and endure a billion more automobiles and human beings in the near future.When does one more straw break a camels back?

Answer 7

because this short set of facts fit in with the agenda.. er... theory.

even then, they were manipulated to show that 1998 was the hottest year, instead of 1934, which has recently been discovered.

how do the ice cores show global warming trends, but also had shown "global cooling" trends in the 70's?

Answer 8

We do ask these things
We use all the proxy data we can to get an idea of how the climate was, how fast it changed, ect.
I'm sure you have heard of ice core samples?

Answer 9

co2science.org