Quote from wjk:
Certainly the ground stations are important, but questions I then ask are: Where are they located? On a hill, in a valley, in the country, in a city, etc? Ground stations are susceptible to an entire array of local effects that have an impact on surface temperature averages.
Tree rings: Was a larger tree ring the result of a wet year, which would possibly have been a cooler year because of cloud cover, or a warmer year causing increased precip? Were there increased nutrients from runoff or atmospheric deposits (opposite for thin rings)? Do these and other surface measurements truly reflect the atmospheric conditions (temps) above the surface to the edge of the atmosphere over a large area during the time period these data are collected from? Certainly they show climate during those periods.
It is interesting to me that we find this increase in atmospheric temp (and surface, of course) beginning around the time we started measuring temp from space...in other words, very accurate and total view of atmospheric temp through altitude. These changes might be reflected in sharp changes in long term data charts. The tech advances may be extapolated out of the charts so as not to skew them. But there is that extrapolation again. So much depends on that, doesn't it? Whether it's tree rings, ice samples, etc. Increased extrapolation means increased likelyhood of error. I think that error potential fades with current methods.
The same accuracy from space gives excellent sea surface temp readings, though not sure regarding deep water reading. That is equally important, but I'm not up on how uniform measurements of deep sea temps are accumulated, so that's for another discussion. I'll stay with atmospheric temps, for now.
So we've have this incredible revolution in temp reading capabilities while at the same time there has been a considerable increase in CO2. Does this show that CO2 caused this warming beyond a shadow of a doubt, or does it show we just better at seeing what those temps were during the same interval? Are we looking at a normal warming cycle in ways we couldn't before, or are we seeing a direct result of trapping? Both? Possibly. As you've indicated, many believe so.
My questions don't dispute the data presented in the charts; they question why the charts say what they say. Long term accurate data means everything, especially if we are going to drastically alter our lives. It would have been nice to have satellite temps data throughout the last century, wouldn't it? Then I would have no problem calling it settled. I know many want to act right now. I'd be content to get another 20-30 years of exremely accurate data, and then draw further conclusions. I know, that's too late in the minds of many. I know most scientists are on board, but weren't there times in the past when most were on board, and it turned out they were wrong as tech advances were made?
We have over 160 years of data from many different thermometers from many different areas sited at different type places. They all show the same rise in temps.
"The instrumental temperature record shows fluctuations of the temperature of the global land surface and oceans. This data is collected from several thousand meteorological stations, Antarctic research stations and satellite observations of sea-surface temperature. The longest-running temperature record is the Central England temperature data series, that starts in 1659. The longest-running quasi-global record starts in 1850.[1]"
There is a scientific consensus that climate change is occurring and that greenhouse gases emitted by human activities are the primary driver.[21] The scientific consensus is reflected in, for example, reports by the Intergovernmental Panel on Climate Change (IPCC) and US Global Change Research Program.[21]
Although the IPCC AR4 concluded that âwarming of the climate system is unequivocal,â public debate over the evidence for global warming continues.[22] However, it is often confined to a small set of reiterated disputes about Land Surface Air Temperature (LSAT) records, diverting attention from the broader evidence basis.[22]
The methods used to derive the principal estimates of global surface temperature trends â HadCRUT3, NOAA and NASA/GISS â are largely independent.[22] So, the spread of the three estimates indicates the likely degree of uncertainty in the evolution of the global mean surface temperature.[22] Independently derived estimates of tropospheric temperature trends for the whole troposphere channel from satellites differ by an order of magnitude more than do estimated surface temperature trends.[22]
Numerous studies attest to the robustness of the global LSAT records and their non-reliance on individual stations.[22] Evidence from recent re-analyses lends further support.[22]
The IPCC conclusion that âwarming of the climate system is unequivocalâ does not rest solely upon LSAT records.[22] These constitute only one line of evidence among many, for example: uptake of heat by the oceans, melting of land ice such as glaciers, the associated rise in sea level and increased atmospheric surface humidity (see the figure opposite and effects of global warming).[22] If the land surface records were systematically flawed and the globe had not really warmed, then it would be almost impossible to explain the concurrent changes in this wide range of indicators produced by many independent groups.[22] The observed changes in a broad range of indicators provide a self-consistent story of a warming world.[22]
[edit]Other reports and assessments
The U.S. National Academy of Sciences, both in its 2002 report to President George W. Bush, and in later publications, has strongly endorsed evidence of an average global temperature increase in the 20th century.[23]
The preliminary results of an assessment carried out by the Berkeley Earth Surface Temperature group and made public in October 2011, found that over the past 50 years the land surface warmed by 0.911°C, and their results mirrors those obtained from earlier studies carried out by the NOAA, the Hadley Centre and NASA's GISS. The study addressed concerns raised by "skeptics"[24][25] including urban heat island effect, "poor"[24] station quality, and the "issue of data selection bias"[24] and found that these effects did not bias the results obtained from these earlier studies.[24][26][27][28]
One of the issues that has been raised in the media is the view that global warming "stopped in 1998".[29][30] This view ignores the presence of internal climate variability.[31][30] Internal climate variability is a result of complex interactions between components of the climate system, such as the coupling between the atmosphere and ocean.[32] An example of internal climate variability is the El Niño-Southern Oscillation (ENSO).[30][31] The El Niño in 1998 was particularly strong, possibly one of the strongest of the 20th century.[30]
Cooling between 2006 and 2008, for instance, has likely been driven by La Niña, the opposite of El Niño conditions.[33] The area of cooler-than-average sea surface temperatures that defines La Niña conditions can push global temperatures downward, if the phenomenon is strong enough.[33] Even accounting for the presence of internal climate variability, recent years rank among the warmest on record.[34] For example, every year of the 2000s was warmer than the 1990 average.[35]
