Global Warming is Man-Made

== Roy’s calculation == Roy’s assumption that warming is linear is simply untrue: Even though CO2 is the dominant climate driver of modern climate-change, it does not mean natural climate variability cannot occur in the system—it does occur. A few ‘pauses’ or unprecedented accelerations do occur. CO2 is logarithmic in relation to temperature. This means that every CO2 doubling has the same effect, even though each molecule warms less. For example, a doubling from 100 ppm to 200 ppm would have the same effect as a doubling from 280 to 560 ppm. Warming will only occur fairly linearly if each doubling occurs at the same rate. His calculation uses faulty assumptions. His 3 degrees C slope is from my former argument that CO2 sensitivity is around 3 degrees C. Sensitivity is for each CO2 doubling. His line begins in about 1970, and CO2 has not doubled from 1970 to now (in terms of the pre-industrial levels). In 1970 there was about 323 ppm of CO2, and in 2014 the number is around 400 [1][2]. So over that time period, CO2 increased 77 ppm. That would only be about 13.2% of a CO2 doubling. So .132 * 3 is about .4 degrees temperature rise since 1970. It has warmed about 0.5 degrees since the 1970s [3]. Therefore when Roy’s calculation is done correctly, CO2 is responsible for 80% of the temperature rise over that time period. == Climate model accuracy == Roy argues that global circulation models (GCMs) are inaccurate. This is untrue. Climate models actually have accurately reproduced temperature since 1900. GCMs cannot replicate warming without a CO2 forcing. GCM’s are only accurate when CO2 forcing is accounted for in hindcasts. This means that CO2 is a large forcing of modern climate. This can be demonstrated with the following graph [4]: Models also reproduced temperatures after the Mt. Pinatubo eruption. They correctly predicted the temporary 0.5 degrees C cooling after the eruption, meaning models can replicate temperature changes due to aerosol and sulfate forcings [4]. A paper published in Nature looked at each 15 year period since the 1950s. Their models were able to accurately produce those trends as well as many El Nino events. The study even commented on the pause. The authors note that the pause does not falsify model accuracy, as it is only “one realization where the decadal natural variability component of the model climate is generally not in phase with observations” [5]. In other words, it is the exception rather than the rule. Models accurately predict warming trends, one exception does not falsify the models. In fact, they note models still were able to predict recent trends in the Pacific—a huge portion of the world. Hansen’s 1988 model, unlike what skeptics claim, shows close correspondence with the actual temperature change. His model seemingly assumes more warming due to the fact he assumed 25% too much climate sensitivity. When the sensitivity is lowered to 3 degrees C, his scenario B correlates perfectly with observed temperatures [6]. The model offers evidence of a 3 degrees C climate sensitivity. Models can accurately hindcast warming which occurred in the last century and models can accurately predict the cooling forcings of aerosols. Further, the 1988 model predictions were correct, indicating that models can predict future temperatures. == The ‘pause’ == The argument that the ‘pause’ disproves global warming is incorrect. The fact that other forcings can *temporarily* blunt the warming effect of CO2 is not a nail in the coffin. Unless Roy denies the greenhouse effect, it is preposterous to claim that CO2 cannot influence temperatures. The fact that natural forcings have caused a short-term ‘pause’ does not disprove AGW. Some models actually have predicted the ‘pause’ [7]. The Met Office has released a report regarding the ‘pause’. They note that the earth’s heat content is still increasing, and is actually increasing faster than ever before. Surface warming has slowed due to the fact that the oceans have been accumulating more heat. This effect is temporary. Eventually, the ocean’s heat content will ‘max out’, and surface warming will resume. So CO2 is still warming the climate system [8]. As noted, this effect is temporary, and as heat continues to accumulate the oceans will warm, and surface temperatures will eventually begin to increase. CO2 forcing has not stopped—its heat is merely being distributed elsewhere. The earth’s surface has stopped warming not due to CO2 not being a greenhouse gas, but rather its heat content being distributed elsewhere. There is still doubt as to whether or not the ‘pause’ is real (as I noted last round). Tamino, a statistician, has worked out the data. Using each possible start date for the ‘pause’, he ran the p-value of statistical significance. For each start date, none of them reach the 95% statistical significance level. Therefore, no matter which data-set you use, no matter what start date you use, there is no proof of a statistically significant slowdown in global temperatures. The following chart [9] details the results: Therefore, there is little proof that a ‘pause’ is occurring at all. == Solar activity == Roy argues the sun caused the LIA and the MWP. I agree! CO2 was fairly stable in those time periods, so it could not have been the forcing. Climate reacts to whatever is forcing it to change at the time. As I convincingly argued (CON’s words), the sun cannot be the current forcing. CO2 has been increasing, and likely is the current climate forcing. I never said that the sun couldn’t affect climate. I merely stated that cosmic rays do not change the climate, and that the sun is not the driver of current climate change. As noted, solar forcing has been decreasing, meaning it cannot be the cause of modern warming. TSI has been falling, GCR’s have been increasing, and solar cycle lengths have fallen as temperature dramatically increased. The sun cannot be the forcing behind the current warming—it is impossible. I have cited many peer-reviewed studies corroborating those conclusions. == Paleoclimate == This entire argument proved that CO2 has the potential to change climate. CON claims I said CO2 does not correlate with temperature. This is a massive misinterpretation. I first cited the study which every paleoclimatologist uses in their datasets, the GEOCARB study. The study found that CO2 did correlate with temperature. I then cited Royer 2006, which noted how CO2 does correlate with temperature when 1) pH effects are corrected for, and 2) the sun is accounted for. The sun does not correlate with temperatures, but it obviously affects climate. It only correlates with temperatures when CO2 forcing is included. Therefore, we can conclude that CO2 is one of the main drivers of past climate. This proves that CO2 has the ability to warm the planet, meaning the increased emissions have had a warming effect. Research using proxy data over the last 500 million years find a climate sensitivity of 3 degrees C [9]. This supports the idea that the modern increase of CO2 concentrations are having a large effect on modern climate. Roy again claims the CO2 lag refutes AGW. I already responded to this. CO2 has lagged temperatures over the previous interglacial periods, I agree. But CO2 acts as an amplifier in those conditions. If CO2 amplifies temperature, it has a warming effect. If it has a warming effect, it can be a forcing. Therefore, CO2 has an effect on temperature, and can be the driving force behind modern climate change. The lag argument was solidly refuted last round. Roy also dropped my argument about CO2 causing the end of the last ice-age. This argument definitively proves that CO2 has a massive impact on temperatures. The fact that it is warmer now than in the MWP demonstrates that the current warming is unprecedented. I have proven that the modern warm period is warmer now than at any point during the past 2000+years. == Burden of proof == Roy claims I have not proven AGW. This is incorrect. When it comes to sensitivity, CO2 has a *direct* effect on temperature: each doubling causes about 1.1 degrees C warming. Using calculations from a skeptical physicist [10], this direct effect means that CO2 has caused over 50% of the recent warming. Sensitivity is likely much higher, about 3 degrees C. With higher sensitivity, CO2 causes more warming. This is corroborated with studies using many different methods. With the high sensitivity proven (R1), CO2 is the main factor of modern climate change. Roy dropped this argument. I proved there was a scientific consensus. This suggests the empirical evidence almost certainly corroborates AGW theory. I proved that CO2 is one of the main forcings in past climate. This is important because it dispels any doubts that CO2 has a large warming potential. In fact, paleoclimate proves 3 degrees sensitivity. Therefore, this also proves that CO2 is the main driver of modern climate change. I have proven that CO2 does change climate. The direct effect of CO2 (which no one disputes) causes over 50% of climate change, and when sensitivity is 3 degrees C, CO2 is the cause of the warming since 1970. I have upheld the BOP. Roy, on the other hand, has failed to explain *why* CO2 is either not a forcing, or that my sensitivity estimate is wrong. He drops the sensitivity argument, conceding that CO2 is the main driver of warming in the modern era. His alternative explanation, the sun, was eviscerated last round. His arguments about a ‘pause’ are also put into question, and his model argument is based upon flawed assumptions. I have, on many occasions, cited Roy’s evidence against him. Low sensitivity proves AGW, high sensitivity proves AGW, and Roy totally ignored that key point. Therefore, I have proven that AGW exists, whereas Roy fails to put a dent into the extremely well supported theory. Thanks for the debate, Roy, it was fun! Please, vote PRO! http://www.debate.org...