Global Warming is Man-Made

== Rebuttals == R1) Solar cycle as a driver of climate It is good that Roy discards the idea that TSI can explain the modern temperature increase. Even skeptical climatologists are beginning to accept this, they note TSI can explain “virtually none” of the warming past 1950 [1]. Roy begins by citing a 1991 study by Friis-Christensen et al (his graph). The study purported to claim the solar cycle length correlated with temperatures. It must be noted Christensen’s temperature data ended in 1985, which ignores a huge portion of the warming which occurred in the 1990s. Christensen’s study was criticized for mathematical errors. A new paper has come out and corrected the errors from the original paper. The result was solar cycle length did not correlate well with temperature. Solar cycle length did correlate with temperatures until 1985—when the dataset for Friss-Christensen et al. ended—but after 1985, the correlation broke apart. Solar cycle length fell as temperatures began to dramatically increase. The correlation Roy uses in his graph has since been falsified [2]. The following graph shows the updated correlation: The mathematical errors are shown by this graph [3]: As can be seen, Roy’s source is flawed and newer measurements prove that solar cycle lengths cannot explain the modern warming. Roy then cites a paper purportedly claiming 72% of the earth’s increase in temperature is due to the solar cycle. Roy cites a skeptical blog, and the blog exaggerated the findings. 72% of the temperature change in the North Atlantic can be explained by solar fluctuations, according to the study—not global temperatures. If you go to the actual source it says “[w]e find for the Norwegian local stations investigated that 25–56% of the temperature increase the last 150 years may be attributed to the Sun” [emphasis added] [4]. You can see the study is looking into local stations, not global phenomena! Roy’s 72% number is an exaggeration and is in relation to one region, not the entire globe. Evidence shows global temperatures do NOT correlate with solar cycle lengths, and much of the evidence Roy uses relies upon local Norwegian data. Not global data. Therefore, Roy fails to prove that the sun correlates well with global temperature. R2) Cosmic rays and climate For cosmic rays to explain climate change, all of the following must be true: 1) the solar magnetic field must have a long-term negative trend, 2) the cosmic ray flux must have a long-term negative trend, 3) cosmic rays must create low level clouds, 4) low level clouds must have a long term negative trend [5]. The solar magnetic field actually has not changed much over the last 30 years. The correlation between temperature and cosmic rays is fairly weak. Even assuming that the correlation exists, it is about equal to the anti-correlation of TSI (which has been falling, and leading to cooling). Cosmic rays have had little overall impact on temperatures over the last few decades [6]. Have cosmic rays had a long-term negative trend? No. Cosmic rays have had no discernable trend from 1951 to 2006, and have stayed relatively stable [5]. Further, the GCR (galactic cosmic ray) flux only correlated with temperature between 1970 and 1985, and even then it lagged temperature. The correlation totally breaks down in the 1990s. The changes in the GCR flux cannot be the cause of more than 15% of the observed temperature increase [7]. In fact, some research has found the GCR flux is increasing. SkepticalScience, quoting Erlykin et al. 2013, notes “[r]ecent measurements of the cosmic ray intensity show that a former decrease with time has been reversed. Thus, even if cosmic rays enhanced cloud production, there would be a small global cooling, not warming” (emphasis original) [5]. If GCR’s have been causing a net-cooling, they cannot explain the warming trend. Do GCR’s cause low-level cloud cover? No. The correlation between GCR’s and cloud cover begins to disintegrate in 1989. By 1994, the correlation completely breaks apart, and there is no way that we can see changes in the GCR flux affecting low-level clouds, as can be seen in the graph [8]. Cosmic rays are red, versus low cloud cover (blue). We see little correlation between the two. Do low-level clouds have a negative effect on temperature? There is conflicting evidence here [5]. Regardless, GCR’s don’t seem to change cloud cover or correlate well with temperature. R3) The ‘pause’ Roy claims surface temperature has shown no trend recently. He is using RSS data. UAH data finds an increase of temperature over the same period [9]. Over such a short time period, it is impossible to get statistically significant results. So in order to reduce data uncertainty, I will change the data to 1970 – present. With this, we will always see a warming trend. However, if this ‘pause’ is significant, we should see a large change in trends. Using HADCRUT4 data, from 1970 – 1996 (‘pause’ began in 1996) we get .153 C/decade with a margin of error of 0.067. Then to see if the ‘pause’ significantly reduces this trend, I now extend the data from 1970 – 2014. What do I get? 0.165 degrees C per decade with a margin of error 0.030 [9]. We see no decrease in the overall trend, which would occur if the ‘pause’ were significant. And this method reduces data-uncertainty. So we see there is no statistically significant slowdown of the warming trend in HADCRUT4 data. The long-term trend of increasing temperatures is due to CO2. Short-term variability happens all the time; it does not mean that the long-term increase is going to stabilize forever. La Nina events have decreased surface warming. La Nina is an oscillation, it is not a long-term phenomena, and will revert to a positive trend eventually. Many models that account for these oscillations do reproduce the ‘pause’. When these factors are accounted for, greenhouse warming still continues to exist [10]. The assertion that models cannot account for the pause is simply incorrect. The oceans increased heat content, aerosol cooling, La Nina events, etc. all lead to cooling. The fact that any warming has happened at all (see my UAH & HADCRUT4 analysis) is supportive of idea that CO2 is a strong climate driver. R4) Paleoclimate Roy begins by claiming CO2 lags temperature. Although he cites no source (or at least, not in that paragraph) I know where he got the claim. I cited the exact paper with that claim last round! It claimed there was an 800 year lag between past climate changes and CO2 concentrations. What skeptics don't tell us—and what the paper actually said—is CO2 still acted as an amplifier to other climate changes (a positive feedback for the orbital forcing of the interglacial cycle). CO2 preceded northern hemispheric deglaciation. If you actually read the papers, which claim there to be a lag, they almost all note how CO2 acts as an amplifier and how the results do not contradict AGW. There is new research (Shakun et al.), which argued that CO2 preceded the end of the last ice age, and may have (in part) led to the warm interglacial in which we live today [11]. The following graph from the study demonstrates how CO2 may have been an important factor in the most recent deglaciation: Blue = temperature, Red (and yellow) = CO2 concentrations. The recent Shakun study demonstrates how CO2 may have, in part, ended the last ice age. Roy goes on to claim there is no correlation between CO2 and past temperatures. I followed his sources. The first one was temperature data and made no comments on correlation. Berner 2001 is the other source. I cited this exact study last round. I pulled a direct quote out of the study. I will reiterate it here, “over the long term there is indeed a correlation between CO2 and paleotemperature” [R2]. Using Roy’s sources, we see that CO2 does correlate with temperatures. Roy’s graph is also a oversimplification. It fails to mention that there ARE other forcings in climate. The other major forcing, the sun, does not correlate well with phanerzoic temperatures either. When the two are put together, there is a strong correlation [12]. The sun alone cannot account for temperatures, and CO2 alone cannot account for the temperatures. When put together, they do. This indicates that CO2 is a very important factor in determining climate. The following graph from the paper depicts the correlation when CO2 and the sun are put together: R5) Consensus I agree with Roy that consensus does not tell us whether or not science is correct. The consensus is not what makes the science clear. But there is a consensus because the science is clear. And Roy claims his data supports solar theory. However, I have adequately dismantled that argument using peer-reviewed research and Roy’s own sources. Roy attempts to claim I have the BOP. This is incorrect. A review of the rules in round one tells us, (rule 5) the BOP is split evenly. Therefore, Roy has an equally important role in disproving AGW as I do in proving it. Roy shows examples of the consensus failing. This can occur, but citing a few high profile cases back when science was less rigorous is not very compelling. Modern science requires empirical evidence for scientific claims. And as most experts believe in AGW, chances are, strong empirical evidence corroborates the theory. Roy makes a claim about catastrophic warming. This is not what we are debating, it is irrelevant. Roy claims climategate shows how scientists ‘suppress’ the science. A reading through the emails, in context, really shows no malice was intended [13]. Multiple independent panels have reviewed the emails, and concluded that no scientific malpractice was committed [14]. Conclusion The sun is not the cause of the recent warming trend. Paleoclimate continues to give credence to the idea that increased CO2 levels warm the climate. Man is the main driver of modern global warming. Sources: http://www.debate.org...