# A call for EVIDENCE regarding human caused global warming **URL:** \ **Category:** Great Debates\ **Created:** [February 24, 2006, 12:25pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912 "2006-02-24T12:25:48Z")\ **Posts on this page:** 8\ **Page:** 3
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [March 9, 2006, 9:31am UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/41 "2006-03-09T09:31:46Z")
> [@intention](#): > > **up until 1980, both papers show that 100% of the temperature changes can be explained by solar changes.** … which is entirely expected when studying _current_ anthropogenic climate change, of course, given the time lag between an increase in greenhouse gas concentration and any subsequent temperature rise. The temperature in the 1980’s might well have been determined by the [concentrations](http://www.ipcc.ch/present/graphics/2001syr/large/02.01.jpg) in the 1960’s or earlier which, as you can see, aren’t _that_ much above the historical equilibrium value of 280 ppm for CO[sub]2[/sub]. The major anthropogenic forcing off equilibrium occurs _after_ this period, and continues its exponential rise today. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 9, 2006, 4:35pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/42 "2006-03-09T16:35:31Z")
**intention** : First of all, as **SentientMeat** points out, it is entirely expected that the second half of the 20th century should witness the transition between climate being dominated by natural (in large part, solar) effects and climate being dominated by the emissions of greenhouse gases. As I noted, close to 60% of the total change in CO2 levels from the pre-industrial baseline has occurred since 1970…and, as **SentientMeat** has noted, there is also an inertial time-lag involved. Furthermore, in the earlier days, the cooling effects of aerosols may have cancelled out some, most, or even more than all of the effect of warming due to greenhouse gases…until such time as the greenhouse gas levels built up high enough (and the Western nations, at least, began to control aerosol emissions enough) that the greenhouse gas effects started to dominate. This is, as I noted in an earlier post, well-summarized by [this](http://www.grida.no/climate/ipcc_tar/wg1/figts-15.htm) graph showing how the best estimates of both natural and anthropogenic factors are needed in the climate models to get good agreement with the observed temperature record, with the anthropogenic part being particularly important to get agreement over the last ~30 years. A few other issues with your latest post puzzle me: (1) Your claim that the papers I linked to show that 100% of the pre-1980 temperature effects can be explained by solar effects is an exaggeration. For one thing, it is well-known that other natural factors such as volcanic eruptions play a role. For another, as the EOS paper discusses in the text, the good (not perfect)agreement in the pre-1980 data is exaggerated by the way the figure (fig. 1a) has been produced, i.e., there are two free parameters corresponding to a shift and scaling of the left vertical axis that have been adjusted to give the best agreement between the solar cycle length and the temperature (not to mention the smoothing issues). So, what they have shown is basically good agreement over one major up-down cycle in temperature. When an attempt has been made, using proxy temperature data, to look at more cycles (as in Fig. 2), it is seen that the relative heights of the oscillations do not agree too well between the solar cycle length and the temperature curves (although I am not sure exactly how strong that conclusion can be made given the uncertainties in proxy temperature reconstructions). (2) You set up “strawmen” with your points 1 and 2. Noone is claiming that solar influence is nil after 1980…but simply that the solar has remained flat while the temperature has risen due to the anthropogenic forcings. Likewise, noone is claiming that the CO2 forcing was nil before 1980 but simply that it was dominated by natural forcings (and probably counteracted in large part also by sulfate aerosols during the middle part of the 20th century). (3) It is amusing to see you embracing your point 3 as the correct explanation even though you previously, in post #17, scorned other authors when you (mistakenly) thought they were claiming that their theory is right and the data is wrong. The surface temperature record is extremely carefully studied and, despite your claim (which you have not even provided support for) about the closing of rural stations, no serious scientific body seems to agree with you that there is any serious question about it. In fact, in 2000, at a time when the surface temperature record and the lower tropospheric temperatures reconstructed from satellite measurements (available since 1979) were in clear conflict, an NAS panel nonetheless [concluded](http://fermat.nap.edu/books/0309068916/html/2.html) that “In the opinion of the panel, the warming trend in global-mean surface temperature observations during the past 20 years is undoubtedly real and is substantially greater than the average rate of warming during the twentieth century. The disparity between surface and upper air trends in no way invalidates the conclusion that surface temperature has been rising.” Since that time, the differences between the surface temperature record and the satellite measurements have basically been reconciled (with the satellite record having been found to be incorrect). The satellite record now shows only a little less or maybe a little more warming than the surface data (depending on whose reconstruction you believe) so there is much less room then than there was previously to question the reality of the warming since 1980. There is also independent evidence of such warming. e.g., in the [proxy reconstruction of temperature based on worldwide glacial retreat](http://www.realclimate.org/index.php?p=129). Yet, you want to dismiss this overwhelming evidence because it disagrees with your pet theory about the sun being the one overwhelming influence on the climate. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 24, 2006, 2:12pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/43 "2006-03-24T14:12:07Z")
> [@intention](#): > > _ **What This Study Means** _ > > After this study came out in November, another study of recent glacier surging around the coast of Greenland was reported last week. That other new study received a lot of hype, saying that it shows that the ice cap is melting, sea levels will soon be up around our ears, and the rest of the usual “the world is melting” nonsense. > > That study, however, needs to be read in conjunction with this one I reference above, which shows that despite the surging, the Greenland Ice Cap has been getting _ **thicker** _ over the same period. > > Regardless of surging, since the ice cap is getting thicker, the Greenland Ice Cap must be _ **gaining ice overall** _, not losing ice. Of course, the usual caveat applies, this is only a short record. But it does indicate that during the time of the recent surging, the amount of ice was constantly increasing. We can cancel the sea level alert, because at the moment, with the snow piling up on top, Greenland is actually lowering the sea level. > > Does this support Human or Natural GW? Neither, directly. It is in fact what we would expect in a warming world, because more heat brings more evaporation, and more evaporation brings more snow and rain. It does indicate, however, that there is no “runaway” heating going on, as the Greenland Ice Cap is increasing, not melting. On this general subject, this week’s issue of science has several articles related to ice sheets and global warming. In particular, [here](http://www.sciencemag.org/cgi/content/full/311/5768/1698) is a News Focus article entitled “CLIMATE CHANGE: A Worrying Trend of Less Ice, Higher Seas” [R. A. Kerr, Science **311** , 1698-1701 (March 24, 2006)]. The upshot of the article is that, although much uncertainty remains about what is happening and what is going to happen with the ice sheets, recent trends are very worrisome. In particular, they discuss the article on glacier surging around the cost of Greenland that was mentioned by **intention** above and then go on to discuss other recent work in ice sheet mass balance in Greenland and Antarctica. Here is an excerpt: > [@](#): > > In another approach to estimating mass balance, researchers sketch the changing shape and therefore volume of the ice sheet. In a paper just out in the Journal of Glaciology, glaciologist Jay Zwally of GSFC and colleagues use satellite radars to measure the height of the Greenland Ice Sheet’s broad plateau and airborne laser altimeters to monitor the height of glaciers draining to the coast, which are too small for satellite radars to see reliably. “We have strong evidence the ice sheet was near balance [during] the last decade of the 20th century,” says Zwally. “Our measures show a slight positive gain of 11 [cubic kilometers] per year” between 1992 and 2002. > > Global warming contrarians have already taken up Zwally’s result as evidence that nothing much is happening with the ice sheet, so there’s nothing to worry about. Zwally disagrees. “There’s no question there’s been an acceleration of some of Greenland’s glaciers over the last 5 years,” after his surveys were completed, he says. “I would say that right now the current loss is 30 to 40 [cubic kilometers] per year,” he says, based on his gut feeling about the most recent radar and laser observations. > > That’s getting close to the mass loss reported last fall using a third approach: repeatedly weighing the ice sheet. Geophysicists Isabella Velicogna and John Wahr of the University of Colorado, Boulder, reported in Geophysical Research Letters how the two satellites of the Gravity Recovery and Climate Experiment (GRACE), flying in tandem, gauge the mass beneath them. They precisely measure the changing distance between them caused by the gravitational pull of the passing ice. Between 2002 and 2004, GRACE found a loss of about 82 cubic kilometers of ice per year. > > All things considered, it seems clear that “Greenland has been shifting to a negative mass balance the last few years,” says glaciologist Richard Alley of Pennsylvania State University in State College. The same can be said for the West Antarctic Ice Sheet. All recent surveys have the far more massive East Antarctic Ice Sheet slowly gaining mass from increased snowfall. But that gain falls far short of compensating for the loss from West Antarctica. There, Zwally’s analysis has the ice shrinking by about 47 cubic kilometers per year. And Velicogna and Wahr, writing in this week’s issue of Science (p. 1754), report a GRACE-estimated loss of about 148 cubic kilometers per year. In West Antarctica, as in Greenland, the culprit is the acceleration of outlet glaciers in recent years (Science, 24 September 2004, p. 1897). ---
**Author:** ![Jelymag](https://avatars.discourse-cdn.com/v4/letter/j/d2c977/32.png) [@Jelymag](https://boards.straightdope.com/u/Jelymag)\ **Post date:** [March 27, 2006, 6:23pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/44 "2006-03-27T18:23:54Z")
Hmmm… I seem to remember talk recently about people who ask impossible questions just to be able to say “HA! You’re WRONG!!!” But I can’t seem to find it. Is this a worthwhile discussion? REALLY… is it? I happen to agree with some that anthropogenic sources of CO2 must at least be altering our climate to some degree… but really… DOES IT MATTER??? Is there anyone out there who can deny that the impending human depletion of fossil fuels is causing and will contine to cause economic, political, and social consequences? (Anybody else been crying at the gas pump lately?) Should we be putting more effort into ending dependence on ANYBODY’S oil? YES… most definitely. Should we do it because it might be causing a warming trend that may in worst-case scenario lead to major alterations of global climate… who cares? We should do it because, like it or not, we’ll eventually be forced to because we have no other option. Oh, and [Cecil agrees with me.](http://www.straightdope.com/columns/060224.html) ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 27, 2006, 7:07pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/45 "2006-03-27T19:07:04Z")
**Jelymag** : I agree that there are many good reasons for us to be weaned from fossil fuels. However, lest you think that there just isn’t enough fossil fuels left to cause a major problem in terms of climate change, I believe the estimates are that if we burn all the remaining available fossil fuels over, say, a hundred years or so, that would be enough to raise CO2 levels from their current value of 380 ppm (and prindustrial value of 280 ppm) up to the neighborhold of 1500-3000 ppm (depending on whether we just burn the conventional ones or go for some of the more unconventional ones like the tar sands in Canada). And, that is a quite nightmarish scenario for the climate. Note, in particular, that the remaining stores of coal, which are more carbon-intensive than oil, are quite significant. ---
**Author:** ![Jelymag](https://avatars.discourse-cdn.com/v4/letter/j/d2c977/32.png) [@Jelymag](https://boards.straightdope.com/u/Jelymag)\ **Post date:** [March 27, 2006, 7:49pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/46 "2006-03-27T19:49:44Z")
Oh, please don’t get me wrong! I’m in agreement about global warming. Variations in global temperatures over thousands of years aside, we are pumping the atmosphere full of CO2 (and NOx and particulate matter and who knows what else) and that’s just not cool. In fact I suspect it will be quite toasty. No, my “We’re going to run out of fossil fuels anyway” argument is one that I like because some folks -the ones who think that we should just keep on drilling because there is just no way that all that automobile and power plant exhaust could be hurting anything or anybody- find it more difficult to argue with. 🙂 ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 27, 2006, 8:35pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/47 "2006-03-27T20:35:16Z")
I see your point although some of these folks tend to say, “Well, the market is great at handling issues of scarcity…It will just raise the price over time and other technologies will become more competitive. So, we can just let it handle that.” Thus, it is still necessary to justify why it is necessary to go beyond the unfettered market. Externalized costs such as climate change are one big reason. I suppose another closer to what you are concerned about could be that, while the market handles scarcity okay in principle, it may not always be as far-sighted as one might desire. I.e., if the resource scarcity crops up rapidly enough relative to the time necessary to develop other technologies, there may not be sufficient investment into these technologies until it is too late to prevent some fairly substantial disruption. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [March 28, 2006, 7:35pm UTC](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912/48 "2006-03-28T19:35:44Z")
> [@Jelymag](#): > > Is this a worthwhile discussion? REALLY… is it? Well, I’ve been lurking and I have to say that I’ve found parts of this thread, at least, to be fairly helpful - I’ve got some grasp of the general issues related to anthropogenic climate change, but in particular, **jshore** ’s posts have been very informative. Thanks! [Previous page](https://boards.straightdope.com/t/a-call-for-evidence-regarding-human-caused-global-warming/345912.md?page=2)