Why should we care about the IPCC predictions from their first report in 1990 when they put out an updated report in 2007? Knowledge advances and we get better information. If you're going to try to shoot down the IPCC then use their current reports, not something that's been superseded since the 2nd report in 1995.
Hansen's 1998 model used a climate sensitivity of 4, which was not a bad value for the time. Now we believe the sensitivity is around 3. If you used 3 for the climate sensitivity in Hansen's 1988 model the results would be closer to what really happened.
How many thousands of years have whole forests burned due to natural causes? My guess would be enough to release way more greenhouse gas than our burning of fossil fuels.
Your guess would be wrong. The difference being that the carbon is forests is carbon that is already in the carbon cycle. If forests don't burn they eventually decay and release the carbon back into the atmosphere anyway. The carbon from fossil fuels is carbon that has been sequestered from the carbon cycle for in most cases 100's of millions of years or more. So it is carbon that was not in the carbon cycle until we added it back in. The proof of the fact that your guess is wrong is that the CO2 level in the atmosphere has never been above around 300 ppmv for millions of years but since the advent of human burning of fossil fuels it has risen to 390 ppmv in a bit over 200 years. That is unprecedented in the existence of the genus homo.
The equatorial region where the Intertropical Convergence Zone is located is where humid air rises and dumps rain and so it quite wet. That's where the rain forests of Africa, Asia and South America are located. The ICZ is where the rising leg of the Hadley Cells is located. Where that rising air comes back down is around 30 degrees latitude (both North and South) and the air has lost most of its moisture so those areas are generally dryer. The equivalent areas in the Americas are the US Southwest and Mexico. In Asia the Middle East into Afghanistan and Gobi Desert. South of the Equator the Argentinian pampas, South Africa and Mid to Southern Australia are the dry areas. The reason those areas are not all the same level of aridness is because of differences in the land/ocean configuration in the area and the presence of mountain ranges and other geological features. Hadley Cell expansion which is thought to be related to climate change would move those areas further poleward hence Southern Europe gets a bit dryer.
Yes, the ice cores show that in coming out of a glaciation the temperature rise leads the CO2 rise. They also show that the temperature drop going into the next glaciation leads the drop in CO2. This shows that CO2 is a feedback of temperature change. But it does nothing to show that CO2 cannot be a forcing for temperature change as well. Show me the science that says if we increase the level of CO2 in the atmosphere artificially that the infrared absorption properties of CO2 won't lead to an increase in temperature. The correlation between temperature changes and CO2 levels in no way proves that CO2 can't be a forcing factor as well.
15 years since what? Certainly not 15 years of a cooling trend. You might be able to get one using the CRU data (the vilified Phil Jones' group) and cherry picking 1998 as your starting year but certainly not starting in 1996.
There may have been some of that in the Working Group II (effects of global warming) and Working Group III (mitigation of global warming) reports but you'll find none of that in the Working Group I (the scientific basis of global warming) report. When the errors have been found they have been admitted and corrected. Do a few minor errors destroy the credibility of the whole report? That's like failing an exam because you missed 5 out of a thousand questions.
From 1965 to 1979 there were 44 papers published on global warming as opposed to 7 on global cooling. Clearly there was more support for global warming then.
I don't think you can make much of a case that it has been significantly warmer than it is now since the end of the Eemian interglacial around 115,000 years ago.
Some in the scientific community have taken the possibility of Anthropogenic Global Warming seriously since the 1950's. I believe there was a paper on the possibilities in 1957. In 1967 President Lyndon Johnson got a briefing on the subject. I've taken it seriously since the late 1980's. Just because you're late to the party doesn't mean it hasn't been going on for a while.
That's a good point. The IPCC report is watered down by the political realities of producing it.
It should also be pointed out that the Himalayan glacier error was in the Working Group II report, the report on the effects of climate change which by its very nature is a bit speculative. I'm not aware of any errors of that nature that have been found in the Working Group I report, the report on the scientific basis for climate change.
Yes, the expansion of the Hadley Cells due to global warming is likely to increase the precipitation somewhat on the southern margins of the Sahara such as the Sahel and in Chad as the article points out. At the same time southern Europe, Italy and Greece appear to be getting a bit dryer. Hadley Cell expansion will tend to shift the desert areas it creates a bit northward (and southward south of the equator).
The IPCC's 2035 statement was an error that they have admitted. That particular statement never got vetted by a glaciologist who would have known it was ridiculous. It was basically on the level of a typographical error, not a scientific error.
2000 years ago, the Sahara was lush green forest...
Not even close. From the Wikipedia article on the Sahara:
The modern Sahara, though, is not lush in vegetation, except in the Nile Valley, at a few oases, and in the northern highlands, where Mediterranean plants such as the olive tree are found to grow. The region has been this way since about 4200 years ago.
Because of global warming there is more heat in the atmosphere and more water vapor as well. That will lead to more energetic weather. This is an expected result.
And 10 years has what to do with climate trends? Not much. A recent paper by Santer et. al. calculated the signal (climate) to noise (weather/natural variation) ratio for climate trends. For 10 years the S/N ratio is less than 1. They found it takes 17 years to be sure the signal is greater than the noise.
Slashdot Mirror
You must not have any kids or relatives that you give a damn about.
Why should we care about the IPCC predictions from their first report in 1990 when they put out an updated report in 2007? Knowledge advances and we get better information. If you're going to try to shoot down the IPCC then use their current reports, not something that's been superseded since the 2nd report in 1995.
Hansen's 1998 model used a climate sensitivity of 4, which was not a bad value for the time. Now we believe the sensitivity is around 3. If you used 3 for the climate sensitivity in Hansen's 1988 model the results would be closer to what really happened.
How many thousands of years have whole forests burned due to natural causes? My guess would be enough to release way more greenhouse gas than our burning of fossil fuels.
Your guess would be wrong. The difference being that the carbon is forests is carbon that is already in the carbon cycle. If forests don't burn they eventually decay and release the carbon back into the atmosphere anyway. The carbon from fossil fuels is carbon that has been sequestered from the carbon cycle for in most cases 100's of millions of years or more. So it is carbon that was not in the carbon cycle until we added it back in. The proof of the fact that your guess is wrong is that the CO2 level in the atmosphere has never been above around 300 ppmv for millions of years but since the advent of human burning of fossil fuels it has risen to 390 ppmv in a bit over 200 years. That is unprecedented in the existence of the genus homo.
The equatorial region where the Intertropical Convergence Zone is located is where humid air rises and dumps rain and so it quite wet. That's where the rain forests of Africa, Asia and South America are located. The ICZ is where the rising leg of the Hadley Cells is located. Where that rising air comes back down is around 30 degrees latitude (both North and South) and the air has lost most of its moisture so those areas are generally dryer. The equivalent areas in the Americas are the US Southwest and Mexico. In Asia the Middle East into Afghanistan and Gobi Desert. South of the Equator the Argentinian pampas, South Africa and Mid to Southern Australia are the dry areas. The reason those areas are not all the same level of aridness is because of differences in the land/ocean configuration in the area and the presence of mountain ranges and other geological features. Hadley Cell expansion which is thought to be related to climate change would move those areas further poleward hence Southern Europe gets a bit dryer.
Yes, the ice cores show that in coming out of a glaciation the temperature rise leads the CO2 rise. They also show that the temperature drop going into the next glaciation leads the drop in CO2. This shows that CO2 is a feedback of temperature change. But it does nothing to show that CO2 cannot be a forcing for temperature change as well. Show me the science that says if we increase the level of CO2 in the atmosphere artificially that the infrared absorption properties of CO2 won't lead to an increase in temperature. The correlation between temperature changes and CO2 levels in no way proves that CO2 can't be a forcing factor as well.
The same place the "climategate" emails came from! How can you trust them?
15 years since what? Certainly not 15 years of a cooling trend. You might be able to get one using the CRU data (the vilified Phil Jones' group) and cherry picking 1998 as your starting year but certainly not starting in 1996.
There may have been some of that in the Working Group II (effects of global warming) and Working Group III (mitigation of global warming) reports but you'll find none of that in the Working Group I (the scientific basis of global warming) report. When the errors have been found they have been admitted and corrected. Do a few minor errors destroy the credibility of the whole report? That's like failing an exam because you missed 5 out of a thousand questions.
From 1965 to 1979 there were 44 papers published on global warming as opposed to 7 on global cooling. Clearly there was more support for global warming then.
I don't think you can make much of a case that it has been significantly warmer than it is now since the end of the Eemian interglacial around 115,000 years ago.
Some in the scientific community have taken the possibility of Anthropogenic Global Warming seriously since the 1950's. I believe there was a paper on the possibilities in 1957. In 1967 President Lyndon Johnson got a briefing on the subject. I've taken it seriously since the late 1980's. Just because you're late to the party doesn't mean it hasn't been going on for a while.
That's a good point. The IPCC report is watered down by the political realities of producing it.
It should also be pointed out that the Himalayan glacier error was in the Working Group II report, the report on the effects of climate change which by its very nature is a bit speculative. I'm not aware of any errors of that nature that have been found in the Working Group I report, the report on the scientific basis for climate change.
When did he say that? I can believe natural variation overwhelming the climate signal for a couple of decades but probably not three.
Yes, the expansion of the Hadley Cells due to global warming is likely to increase the precipitation somewhat on the southern margins of the Sahara such as the Sahel and in Chad as the article points out. At the same time southern Europe, Italy and Greece appear to be getting a bit dryer. Hadley Cell expansion will tend to shift the desert areas it creates a bit northward (and southward south of the equator).
The IPCC's 2035 statement was an error that they have admitted. That particular statement never got vetted by a glaciologist who would have known it was ridiculous. It was basically on the level of a typographical error, not a scientific error.
{Grin}
Yeah, right. There is little rain there because that's where the downward branch of the Hadley Cells occurs.
Changes in precipitation with climate change [PDF] by Kevin Trenberth.
Yep, I doubt it's astronomy or geology.
2000 years ago, the Sahara was lush green forest ...
Not even close. From the Wikipedia article on the Sahara:
The modern Sahara, though, is not lush in vegetation, except in the Nile Valley, at a few oases, and in the northern highlands, where Mediterranean plants such as the olive tree are found to grow. The region has been this way since about 4200 years ago.
Before that it was mostly savannah, not forest.
Sometimes it's entertaining to read you guys who don't have a clue what you're talking about.
Because of global warming there is more heat in the atmosphere and more water vapor as well. That will lead to more energetic weather. This is an expected result.
All of those things are true but it's true that there was a record amount of rainfall as well.
Global warming is encompassed in climate change, as is weird weather. You can disbelieve all you want but the climate doesn't care.
And 10 years has what to do with climate trends? Not much. A recent paper by Santer et. al. calculated the signal (climate) to noise (weather/natural variation) ratio for climate trends. For 10 years the S/N ratio is less than 1. They found it takes 17 years to be sure the signal is greater than the noise.