AGW vs. Climate Change Who stands for which and why?

Question

AGW in this question will be for man-made climate change. Climate change will be for a natural cycle. I would like for everyone with interest to give the reasons they feel our current warming is AGW or a natural cycle. Don't just say I think it's natural or AGW. I want to know good scientific justifications for both. I always here for people to disprove AGW so now I want to know exactly why it is those people believe it is AGW.

Mr. Jello: Your stats are a little off but your right in the fact that the sun has contributed to the earths warming. As stated in this article below the sun has definitely contributed to the warming over the past 150yrs. It states only a third of the current warming can be attributed to the sun. I'm not sure whether only a third is accurate I feel it is more.

Dana: Since we have found out that the sun is for sure responsible for a third of the warming, I don't feel that the extra 100ppm of CO2 in the atmosphere is all contributed by humans. If humans did start the warming then this means that ocean started warming as well and released even more CO2 than average. So the extra 100ppm of CO2 can be accredited to both human and the ocean. You cannot say that the warming is all man when clearly it is not!!

Here's the link that I forgot to add.

http://www.oar.noaa.gov/spotlite/archive/spot_sunclimate.html

Answer 1

Just because the greenhouse gases increased to 380 ppmV does not mean that humans were responsible for the total increase. In fact CO2 levels increase naturally following warming. CO2 has not been shown to drive climate change, yet the climate changed, is changing, and always will based on the Milankovitch cycle as well as shorter term cycles in the sun's output and magnetic variances. It has been warming generally for the last 10,000 years with minor periods of warming and cooling. We are currently in a long term and short term warming trend. There is no indication that this is from man-made greenhouse gases except that humans have added greenhouse gases, greenhouse gases have increased in concentration, and they should be expected to absorb radiation and increase warming. The amount that added CO2 adds to the warming is what should be in contention and whether it represents a crisis. I think that it might add a bit to the warming trend but it is not a significant crisis.

Answer 2

Scientists have tried very hard to explain the present warming as natural. The problem is that the numbers don't work. In scientific terms the "natural" theories may sound good, but they're not QUANTITATIVELY correct.

Check out these graphs. The blue shows what happens if you only consider natural factors, the pink adds in man made greenhouse gases. It's not hard to see the blue just doesn't work and the pink does.

http://environment.newscientist.com/data/images/ns/cms/dn11649/dn11649-1_688.jpg

Additional discussion is here:

http://environment.newscientist.com/channel/earth/climate-change/dn11649

Another reason scientists know this warming is not natural is the relationship between CO2 and temperature. In the past warming was mostly caused by the Sun. CO2 levels didn't rise until hundreds of years later as warming ocean waters released CO2. This time they are going up at the same time, because CO2 is causing the warming.

There are other reasons, those two seem most impressive to me. The bottom line (note the key word, quantitative):

"There's a better scientific consensus on this [climate change] than on any issue I know -
Global warming is almost a no-brainer at this point,You really can't find intelligent, quantitative arguments to make it go away."

Dr. Jerry Mahlman, NOAA

Skeptics have "logical" arguments that this is natural. Global warming scientists have the data.

Answer 3

The current warming is not part of a natural cycle. We're currently warming 20 times faster than when the Earth naturally comes out of an ice age while we should be in a very stable portion of the cycle. Here you can see coming out of the last ice age, the planet warmed about 7°C in about 8,000 years (0.00087°C per year)

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

Currently we've warmed about 0.5°C in the past 30 years (0.0167°C per year).

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

On top of that, according to orbital cycles, 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

And solar output has decreased over the past 30 years.

http://news.bbc.co.uk/2/hi/uk_news/6290228.stm

There's too much evidence in support of the AGW theory for me to discuss it all here. Bottom line is that the only way to explain the rapid acceleration of global warming is for human greenhouse gas emissions to be primarily responsible. Bob's graphs linked below illustrate this nicely.

Also, contrary to jim z's claims, isotopic analysis proves that essentially all of the atmospheric CO2 increase has been due to human emissions.

And not surprisingly, Jello's math is completely wrong. The increase from 280 ppm to the current 387 ppm is a 38% increase in atmospheric CO2. I have no idea how he gets 0.001% out of a 38% change (off by a factor of 38,000) - he probably flunked grade school math (is Jello smarter than a 5th grader?). I don't know where he gets this claim that solar output has increased by 0.1% either, since he provides no evidence or even a timeframe over which this change has supposed to have occurred. He might as well claim that moose flatulance has increased 653.487%, so that's clearly what's causing global warming. Even if his 0.1% claim were somehow true, he provides no evidence that this is sufficient to account for the recent warming, except the vastly incorrect statement (on several levels) that the solar increase is 100 times greater than the greenhouse gas increase.

Basically the only thing Jello said that wasn't completely wrong is that atmospheric CO2 concentrations used to be 280 ppm. So he got about half of one sentence right.

Answer 4

Man has caused the amount of co2 to increase from 280 ppm to 360ppm, or less than 0.001%. This is too small to cause any change to the climate.

The Sun has changed 0.1%, or 100 times more than green house gasses. This is significant to cause the 1degree increase from the last 100 years that we are experencing now.