what evidence do scientist have global warming?

Answer 1

If it's known that it is warming, and by how much, then you should be able to determine what the temperature will be dependent on the concentration of co2.

But you can't.

Even though co2 is being pumped out by China, and India, temperatures have gone down every year since 1998.

The only premise believers have is that co2 traps heat, man produces co2, man causes global warming. They deliberately dismiss the Sun as a heat source because it doesn't fit what they want to believe.

And there is pressure to come to the conclusions that are desired. The UN at this time is planning to make it a crime if you don't accept their version of "global warming". Others like The Weather Channel's Heidi Cullum want to see people fired for not accepting their beliefs. It's 1924 Germany all over again!

Answer 2

Basically we know it's warming, and we've measured how much:

http://www.ncdc.noaa.gov/img/climate/research/2005/ann/global-blended-temp-pg.gif

Scientists have a good idea how the Sun and the Earth's natural cycles and volcanoes and all those natural effects change the global climate, so they've gone back and checked to see if they could be responsible for the current global warming. What they found is:

Over the past 30 years, all solar effects on the global climate have been in the direction of (slight) cooling, not warming. This is during a very rapid period of global warming.

http://news.bbc.co.uk/2/hi/uk_news/6290228.stm
http://www.pubs.royalsoc.ac.uk/media/proceedings_a/rspa20071880.pdf

So the Sun certainly isn't a large factor in the current warming. They've also looked at natural cycles, and found that we should be in the middle of a cooling period right now.

"An often-cited 1980 study by Imbrie and Imbrie determined that 'Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6,000 years ago will continue for the next 23,000 years.'"

http://en.wikipedia.org/wiki/Milankovitch_cycle

So it's definitely not the Earth's natural cycles. They looked at volcanoes, and found that

a) volcanoes cause more global cooling than warming, because the particles they emit block sunlight

b) humans emit over 100 times more CO2 than volcanoes annually

http://www.gaspig.com/volcano.htm

So it's certainly not due to volcanoes. Then they looked at human greenhouse gas emissions. We know how much atmospheric CO2 concentrations have increased over the past 50 years:

http://en.wikipedia.org/wiki/Image:Mauna_Loa_Carbon_Dioxide.png

And we know from isotope ratios that this increase is due entirely to human emissions from burning fossil fuels. We know how much of a greenhouse effect these gases like carbon dioxide have, and the increase we've seen is enough to have caused almost all of the warming we've seen over the past 30 years (about 80-90%). You can see a model of the various factors over the past century here:

http://en.wikipedia.org/wiki/Image:Climate_Change_Attribution.png

This is enough evidence to convince almost all climate scientists that humans are the primary cause of the current global warming.

Answer 3

The conclusive and undeniable proof lies in the ability of greenhouse gases to retain heat. This is a simply physical property they possess and can easily be demonstrated in any science lab.

There's a whole cacophony of circumstantial and indicative evidence such as rising sea levels, retreating glaciers, warmer temperatures etc but these are merely indicators that something is happening, in themselves they're not the absolute proof of what causes global warming - the greenhouse gases are.

- - - - - - - - -

EDIT: TO MR JELLO,

You'll be pleased to know that we can determine the temperature based on concentrations of CO2 and if it was as simple as that then we could make accurate future predictions. CO2 is just one of several greenhouse gases, it's a component of several mechanisms, is a coupled process, subject to variability dependent on other influencing factors, we don't know how much we'll be producing in the future, we can't accurately predict the additional increase due to feedback mechanisms etc etc. You're attempting to over simplfy a complex issue and in the process are eliminating many key factors.

Temperatures have not gone down every year since 1998. Now, if I were to compare current temperatures to a specific year you'd accuse me of cherry picking (as you have with several people in the past), why is it OK for you to cherry pick but not other people?

That aside, 1998 was the hottest year on record according to some temperature records (and you'll be pleased to know that the one I'm finalising now also has 1998 as the hottest year) but temperatures most certainly have not gone down every year since. 1998 was a particularly warm year as was 2005, 1996 and 2004 were cool years. By themselves they're isolated and meaningless, climate is not about individual years or specific places, it's about long term trends. When we look at the long term (25 year) trend we find that the average global temperature has been rising for 40 consecutive years. Looking at the mid term (10 year) trend and the short term (5 year) trend then the same picture emerges.

Nobody dismissies the Sun as a heat source, I'm not sure why you keep saying that, surely you wouldn't want to be accused of deliberately misleading people. The Sun is responsible for virtually all the heat we receive (99.98%).

Greenhouse gases do not generate heat, they retain it. The more there are, the more heat is retained - it's a remarkably simple concept to get your head around and it's also one that can be very easily proven and that no skeptic even attempts to refute. You'll know that skeptics generally avoid using science, facts, figures or anything that can be proven or disproven and like to base their arguments on ideas, opinions and abstract concepts.

Answer 4

The scientific data. It's an enormous database, so I have no other choice but to list links. And even they are just three nice summaries with secondary references.

http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution.png
http://ipcc-wg1.ucar.edu/wg1/wg1-report.html
summarized at:
http://www.ipcc.ch/SPM2feb07.pdf
http://www.globalwarmingart.com/wiki/Image:Carbon_History_and_Flux_Rev_png

All other proof flows from the data.

In words: The temperature of the planet has been generally rising for about 100 years, with an increase in the trend after 1975.

CO2 levels are rising simultaneously. That's different from any other warming in history, because in previous warmings CO2 lagged behind. That was because CO2 was not the primary cause, but mostly an effect. Basic science shows it can be both.

Because of the data and the lack of good arguments against mostly man made global warming, there's a scientific consensus which is very powerful.

http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change
http://www.sciencemag.org/cgi/content/full/306/5702/1686

Good websites for more info:

http://profend.com/global-warming/
http://environment.newscientist.com/channel/earth/dn11462

Yoda - I don't support carbon credits as a way to justify yourself. I do conserve energy and buy wind power credits from my power company. Those things are no-brainers, given the multitude of problems with fossil fuels.

Answer 5

Well, I think we all know that the heat is not coming from Alpha Centari. No one ever dismissed the sun as a heat source. People are dismissing the sun as a major influence to the recent, unusual warming.

Jello is trying to redirect the debate to a topic for which there is no disagreement.

Answer 6

Yeah exactly. Global warming is a myth. It was created by the media to continue their agenda of being anti-oil. There have been many different periods of climate throughout history. Times of global cooling and now warming. It goes in cycles. Plus if there is anyone to blame its the hippies.

Answer 7

Yea a lot of data that you don't know where they got and how much has been skewed toward their belief or desire to keep the funding coming. Scientists are not perfect beings descended from the gods.

Answer 8

Poor Bob. He's already bought his carbon credits from Al Gore.