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We should reply in a strictly fact-based way, using official sources, and being careful not to speculate or over-complicate the matter. Here is my shot at it.
At a recent meeting of a local discussion group a well-spoken retired teacher presented a list of important issues that, in his opinion, have received less coverage by the media than they deserve. "Climate Change" was on his list.
He said it was unfortunate that the main proponent of human-caused "Global Warning" was a prominent Democrat (former VP Al Gore), because that led to the issue becoming politicized, with his fellow Democrats on one side and Republicans on the other. He speculated that had a leading Republican promoted the same issue, the reaction would probably be the reverse.
He then raised several points, citing the NASA Goddard Institute for Space Studies (GISS), the UN Intergovernmental Panel on Climate Change (IPCC), and other expert sources. He said that Global Warming is really happening, with a rise of over 0.7⁰C, and we humans are the main cause due to our massive use of fossil fuels that generate atmospheric CO2, a greenhouse gas that warms the Earth.
During the discussion period I agreed that global warming is real, that atmospheric CO2 undoubtedly causes warming, and that some of the increased CO2 is certainly due to human actions. However, I pointed out that, although atmospheric CO2 levels continue to rise, and at an accelerating rate, global temperatures have not statistically increased for at least 15 years. Therefore, while CO2 levels have definitely caused some of the warming, and rising CO2 is mostly caused by human activities, CO2 cannot be the main cause.
The presenter assured me that he respected my opinions, but, while he was not a scientist, he was relying on scientists and scientific organizations that had studied the issue. He then read a few quotes, including one that said human actions were likely to lead to a "tipping point" where the ice caps melt and there is runaway warming on a catastrophic scale.
I have prepared the following strictly fact-based response, using sources the presenter himself mentioned and being careful not to speculate or over-complicate the matter.
1- It is undoubtedly true that average surface temperatures have increased significantly since 1880. Human activities are responsible for some portion of that warming. [The image below is the latest GISS Global Temperature Index anomaly. The black squares indicate the mean temperature anomaly for each 12-month calendar year. The thick red line indicates the mean temperature anomaly smoothed over 60 months (five years). This graphic shows a net increase of about 0.8⁰C (about 1.5⁰F) since 1880. While I think "data adjustments" have increased the apparent warming by a few tenths of a degree, I accept that warming since 1880 is at least 0.5⁰C (about 1⁰F)]
|Source: http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.pdf - downloaded 6 Sep 2014|
2- Atmospheric CO2 levels have risen steadily, and the rate of increase has doubled since reliable CO2 data from Mauna Loa became available around 1959. [The image below is the latest NOAA ESRL Atmospheric CO2 showing an increase of about 1 ppm/year in the 1960's and about 2 ppm/year in the 2000's. The current level is approaching 400 ppm. The pre-industrial level is estimated to have been about 280 ppm.]
|Source: http://www.esrl.noaa.gov/gmd/ccgg/trends/ - Downloaded 6 Sep 2014. Annotations in purple by Ira.|
⁰C (more than 1⁰F) cooler than the middle of the predicted range, and even 0.3⁰C (more than 0.5⁰F) cooler than the lower edge of the predicted range. Also note that the thick black line falls well below the yellow band, which indicates that the statistical 95% confidence level claimed for the IPCC climate models is not valid. Over the most recent 15-year period, actual satellite temperature observations have consistently been cooler than the central prediction of the IPCC climate models, by from 0.2⁰C to 0.8⁰C (about 0.4⁰F to 1.5⁰F).
4- According to the NASA GISS Global Temperature Index, when smoothed over a calendar year, there has been no net warming for 15 years. Even when smoothed over a longer period of five years, there has been no net warming for seven years. [The image below is a close-up of the upper right corner of the first image in this posting.]
All of the above facts and data is directly from official, government-sponsored climate research organizations, and I have provide web links so anyone can check them his- or herself. If any reader thinks I have distorted or misrepresented any of the above material I will appreciate it if he or she posts a comment to this blog detailing any objections. (If you cannot figure out how to post a blog comment, please send your material to me in an email to firstname.lastname@example.org and I will be happy to post it for you.)
Unlike the above, the following conclusions involve some speculation on my part.
a- Politicization of the issue. I agree that "Climate Change" and "Global Warming" have been way over-politicized. Had the main proponent been a Republican, positions might have been reversed. However, I cannot imagine any Republican President or VP or other Republican office-older of similar national prominence falling for the idea that we humans are responsible for the majority of the warming we have experienced, or that the warming process is likely to lead to global catastrophe. And, even if he or she went along with the initial dire predictions, any reasonable and responsible politician (of either party) would understand that the absolute disconnect between actual temperature observations and predictions of IPCC climate models invalidates the idea of human-caused catastrophic climate change, and reverse their positions.
b- Activists in the catastrophic climate change industry purposely misrepresent the views of responsible Skeptics by making a number of false claims:
- FALSE CLAIM - Skeptics do not believe the basic science of the Atmospheric "greenhouse" effect. RESPONSE - We do accept that water vapor, CO2, and other 'greenhouse" gases are responsible for the Earth being around 33⁰C (60⁰F) warmer than it would be if there were no "greenhouse"gases in the Atmosphere. However, based on the failure of the IPCC climate models to comport with actual temperature observations for at least 15 years, we question the IPCC position that doubling of CO2 will warm the Earth surface by 1.5⁰C to 4.5⁰C (3⁰F to 8⁰F). For example, I believe the true value (called "climate sensitivity") is only a half or a third of what the IPCC claims.
- FALSE CLAIM - Skeptics do not believe the Earth surface has warmed significantly since 1880. RESPONSE - We do accept that average global surface temperatures have increased by at least 0.5⁰C (1⁰F) since pre-industrial times. Many of us think that the thermometer record is somewhat unreliable. It is a matter of official record that, in recent decades, old temperature data prior to the 1970's have been adjusted down by as much as 0.3⁰C (0.5⁰F) and date after the 1980's adjusted up, which has increased claimed net warming by a few tenths of a degree. NASA GISS and other official record-keepers say these "data adjustments" are valid, but many of us think they are self-serving. However, we could be wrong, and the net warming since 1880 might be as much as 0.8⁰C (1.5⁰F).
- FALSE CLAIM - Skeptics do not believe that human activities have any part in causing the warming. RESPONSE - We do accept that unprecedented burning of coal, oil, and natural gas, and some changes in land use, are responsible for a significant fraction of the actual warming. However, based on comparison of actual temperature observations with IPCC climate models, I am convinced that the majority of warming is due to natural causes and processes not under human control or influence.
Looking forward to your comments.