# The Defect in the "Climate Has Always Changed" Argument **URL:** \ **Category:** Great Debates\ **Created:** [February 19, 2017, 7:54pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246 "2017-02-19T19:54:59Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [February 21, 2017, 6:00am UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/41 "2017-02-21T06:00:29Z")
> [@jshore](#): > > To be fair, I think it is about 1/3 of the driving force that is provided by CO2, with the rest provided by the albedo changes due to changes in the ice sheets and vegetation … Just a few points to keep the record straight. There are actually a whole host of different radiative forcings affecting the climate, mostly positive, some negative. [This is a fairly good graphical summary of the main ones](http://www.realclimate.org/images/ipcc_rad_forc_ar5.jpg). You mention albedo changes due to ice sheets and vegetation. It’s important to note that albedo changes are in two distinct categories: forcings and feedbacks, and need to be kept separate because they’re fundamentally different. An albedo forcing is an independent factor that drives the climate in and of itself – the primary example is land use and land cover changes from human activity, which you’ll find in the above chart. Ice cover changes, however, are feedbacks that are a direct consequence of Arctic warming and which amplify that warming when ice cover is reduced. They’re like the increase in water vapor that amplifies CO2 warming. Because they’re feedbacks intrinsically tied to the underlying forcings, these things don’t appear on the chart, but they’re obviously of critical importance in computing and modeling how climate responds to forcings. > [@jshore](#): > > And, this brings us to one important point that I haven’t seen explicitly made here: The fact that climate has changed in the past in response to various forcings is what allows us to (admittedly imperfectly) determine how sensitive the climate is to a certain magnitude of forcing (measured in W/m^2)…And, the forcing due increases in greenhouse gases is quite accurately known, say within 10 or 15%. Namely, a doubling of CO2 results in about 4 W/m^2 of forcing. Good point about climate sensitivity. Climate sensitivity is the measure of how much a given level of forcing will actually change the global average temperature under specified conditions, and is essentially a computation of forcings and all associated feedbacks on the earth’s total energy balance; the most common measure is equilibrium climate sensitivity which is defined as the temperature increase at equilibrium resulting from a doubling of CO2. Yes, the fact that we can observe the effects of CO2 changes in the paleoclimate record helps us estimate ECS, but it’s not the only source of input. We also have extensive modeling runs, the modern instrumental record, and other sources that all have strengths and weaknesses. As a side note, ECS is a temperature delta so its unit is °C, not W/m[sup]2[/sup] which is a unit of the underlying forcing. After decades of research and refinement its estimated value remains basically unchanged at about 2 to 4.5 °C with a most probable value of about 3°C. ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [February 21, 2017, 7:37am UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/42 "2017-02-21T07:37:43Z")
> [@bump](#): > > I mean, something with enough… oomph(?) to affect the Earth’s climate is unlikely to be something that skates in under the radar- it should be something we can measure in some way and quantify, just as we have measured the temperature changes. And the only candidate at the moment that I’m aware of is fossil fuel use. Paleoclimatologists opine that man’s influence on the climate started much earlier than that, when we started slash-and-burn clearing of forests for agriculture and generally burning stuff to keep warm ; some even believe that it’s only \*because \*we’ve been doing that at a specific point in time waaaaay back when that we’re not in an Ice Age right now. Of course digging up older stuff to burn tipped the scale further, faster ; not to mention releasing high altitude sheets of hot CO2. ---
**Author:** ![marshmallow](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@marshmallow](https://boards.straightdope.com/u/marshmallow)\ **Post date:** [February 21, 2017, 8:58pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/43 "2017-02-21T20:58:21Z")
> [@igor\_frankensteen](#): > > In order to declare with certainty that human generated pollution is NOT the current causational factor, they need to come up with another one. This doesn’t logically follow. All that would be required is to show that AGW doesn’t fit the facts. An alternative explanation would be nice, but not necessary. What I notice in the psychology of “climate is always changing” types is a blase attitude that everything will work out anyway. They’re right that climate was a lot different in the ancient past, but a great many of those eras would be a disaster for human civilization. ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 21, 2017, 10:29pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/44 "2017-02-21T22:29:34Z")
> [@](#): > > However, all indications are, that all of the previous similar fluctuations were due to world-wide calamitous problems. Asteroid strikes, super-volcano explosions, and so on. By this I assume you mean in short time periods. If so, this just isn’t true. The very first one (well, one of the first ones) was simply the creation of oxygen over millions of years, changing the atmosphere and causing a mass extinction. There have also been other examples of fluctuations over long time periods (ice ages, snow ball earth, a couple of long term volcanic episodes coupled with large, slow burning coal fields such as the Siberian traps and the like). > [@](#): > > In order to declare with certainty that human generated pollution is NOT the current causational factor, they need to come up with another one. And we haven’t seen any great asteroid strikes, and we haven’t seen any super-volcano explosions. Yet. I’m pretty sure that human generated pollution IS the current highest causation factor. I think the key part you might be missing (I’m unsure since your OP is a bit confusing) is that, even though there have been climate changes such as are happening today, most of the ones that aren’t the sorts of catestrophic rapid event you are talking about happened over millions of years. THIS one is happening in a geological eye blink…and that’s what makes it more frightening to many. > [@](#): > > The Defect in the “Climate Has Always Changed” Argument I think the ‘defect’ here is that Climate HAS always changed…but, usually, not so rapidly. And that’s the key difference this time. Obviously, some of those cataclysmic events you described (asteroid strikes, super volcanoes, Trump being elected, etc) happened even more rapidly. But USUALLY when the climate shifts as we are seeing it today it does so over much longer time periods. The earth has been much warmer than it is today, so it’s not the temperature per se…it’s how rapidly we’ve moved in the last 200 years that’s scary. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 22, 2017, 3:12pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/45 "2017-02-22T15:12:26Z")
It’s all scary until we ask to see the math … ---
**Author:** ![XT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xt/32/456_2.png) [@XT](https://boards.straightdope.com/u/XT)\ **Post date:** [February 22, 2017, 3:30pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/46 "2017-02-22T15:30:03Z")
> [@watchwolf49](#): > > It’s all scary until we ask to see the math … Yeah, it’s certainly difficult to see that 1+1=2. To some, math IS pretty scary… 😛 ---
**Author:** ![Budget\_Player\_Cadet](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/budget_player_cadet/32/205_2.png) [@Budget\_Player\_Cadet](https://boards.straightdope.com/u/Budget_Player_Cadet)\ **Post date:** [February 22, 2017, 3:45pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/47 "2017-02-22T15:45:51Z")
> [@watchwolf49](#): > > It’s all scary until we ask to see the math … At which point it moves to terrifying. For example, comparing the estimated costs of preventing climate change (huge) vs. the projected costs of unabated climate change (fuckmothering ginormous). ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 22, 2017, 4:21pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/48 "2017-02-22T16:21:36Z")
> [@Budget\_Player\_Cadet](#): > > At which point it moves to terrifying. For example, comparing the estimated costs of preventing climate change (huge) vs. the projected costs of unabated climate change (fuckmothering ginormous). Post a link to those projections … I’m curious how actuaries divide up the cost of converting to nuclear powered electric transportation infrastructure between mitigating the cost of when we run out of fossil fuels and/or some yet-to-be-defined climate change … I thought it was interesting this past fire season in The West that forest managers were specifically downplaying the causes due to climate change and were refocusing on the cause of excess fuels due to decades of fire suppression … very little of the cost of these major fires is due to rising temperatures … And don’t forget return on investment … putting up solar cells on our roofs saves us money … and after so many years or decades the investment will pay for itself … the act of mitigating climate change in the long run will be profitable … Let’s see the math here … ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [February 22, 2017, 4:36pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/49 "2017-02-22T16:36:44Z")
> [@watchwolf49](#): > > I thought it was interesting this past fire season in The West that forest managers were specifically downplaying the causes due to climate change and were refocusing on the cause of excess fuels due to decades of fire suppression … very little of the cost of these major fires is due to rising temperatures … Forest fires like those - as opposed to the human-set ones in Amazonia, Indonesia, and elsewhere - are CO2-neutral in the long term. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [February 22, 2017, 5:51pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/50 "2017-02-22T17:51:45Z")
> [@watchwolf49](#): > > Post a link to those projections … I’m curious how actuaries divide up the cost of converting to nuclear powered electric transportation infrastructure between mitigating the cost of when we run out of fossil fuels and/or some yet-to-be-defined climate change … > > I thought it was interesting this past fire season in The West that forest managers were specifically downplaying the causes due to climate change and were refocusing on the cause of excess fuels due to decades of fire suppression … very little of the cost of these major fires is due to rising temperatures … > > And don’t forget return on investment … putting up solar cells on our roofs saves us money … and after so many years or decades the investment will pay for itself … the act of mitigating climate change in the long run will be profitable … > > Let’s see the math here … [https://www.washingtonpost.com/news/energy-environment/wp/2016/12/22/the-coming-battle-between-the-trump-team-and-economists-over-the-true-cost-of-climate-change/](https://www.washingtonpost.com/news/energy-environment/wp/2016/12/22/the-coming-battle-between-the-trump-team-and-economists-over-the-true-cost-of-climate-change/) > [@](#): > > The cost of climate change > > Scientists agree that climate change could cause a wide variety of damages to human communities, including natural disasters, harm to human health, reduced agricultural output and lower economic productivity, all of which result in monetary costs to society. The social cost of carbon, then, refers to the cost of emitting one ton of carbon dioxide into the atmosphere. > > A U.S. government working group first convened in 2009 to develop a method for quantifying the social cost of carbon, and the value has since been used to help create a variety of federal environmental regulations, including the Clean Power Plan. The cost is currently set at about $36 per ton of carbon dioxide. > > For an administration that has promised to reduce regulations on oil and gas operations and revive the coal industry, doing away with — or at least reducing — the social cost of carbon is an obvious priority. The higher the cost is set, the more harm the government assumes will be caused by greenhouse gas emissions, which would generally justify more, rather than less, stringent regulation of the fossil fuel industry. > > Yet many climate experts now believe the social cost of carbon should actually be even higher than the current estimate. The old models used to calculate the value rely on dated research, they’ve argued, and there are certain climate-related damages that may not be adequately factored in. > > “When the U.S. government issued the social cost of carbon first in 2009 or 2010, it was a very good job of summarizing the literature as it stood,” said Michael Greenstone, an economist at the University of Chicago and former chief economist for President Obama’s Council of Economic Advisers, who helped convene the first federal working group to address the social cost of carbon. “What has emerged since then has been an explosion of research to estimate the likely damages from climate change.” > > One 2015 paper argued that the models don’t do enough to account for the effect of higher temperatures on GDP. Once the authors factored it in, they found that the social cost of carbon skyrocketed up to about $220 per ton of carbon dioxide. > > The lead author of that paper, Frances Moore of the University of California Davis, is now working on new research that addresses the impacts of climate change on agricultural output, and how those effects can radiate through the economy. > > “The representation of those impacts in the agricultural sector is pretty dated in the models,” Moore said. “When we update those…we find the social cost of carbon goes up substantially.” > > Other recent research suggests that a majority of climate-focused economists would agree that the social cost of carbon could be set higher. One 2015 study surveyed experts who’d published a climate change-related article in a leading economics or environmental economics journal in the past two decades. The survey, which asked a variety of questions about climate change, found that more than half the respondents thought the current estimate of the social cost of carbon was too low. Eighteen percent thought it was about right, while just eight percent thought it should be even lower. > > The same survey also found respondents generally predicted higher economic impacts from future climate change than past surveys have indicated, which may illustrate our evolving understanding of how climate change will affect human societies. More recent economical studies do show a lot of lost opportunities if we continue in the same path or a worst one as Trump and minions want. [http://web.stanford.edu/~mburke/climate/](http://web.stanford.edu/~mburke/climate/) > [@](#): > > The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change11,12, with important implications. If future adaptation mimics past > adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 > and widening global income inequality, relative to scenarios without climate change. > > In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate. ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [February 22, 2017, 7:47pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/51 "2017-02-22T19:47:43Z")
> [@Quartz](#): > > Forest fires like those - as opposed to the human-set ones in Amazonia, Indonesia, and elsewhere - are CO2-neutral in the long term. Isn’t anything strictly plant-related CO2 neutral in the long run ? They suck it up to grow, then release it back when they burn, get eaten by bugs or die and decompose. The only CO2-positive application of forests is IKEA - provided those Künen last forever and don’t ever decompose. (I’m no scientist by any stretch of the word, mind - I’m going by high school bio here) ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 22, 2017, 7:49pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/52 "2017-02-22T19:49:11Z")
> [@Quartz](#): > > Forest fires like those - as opposed to the human-set ones in Amazonia, Indonesia, and elsewhere - are CO2-neutral in the long term. The specific forest fires I’m speaking about are the ones that burn much hotter than a natural forest fire … such that the fire kills the trees … the past five years the headlines have been screaming “catastrophic climate change” … now that the hysteria is passing I’m hoping a return to the science we are sure about … > [@GIGObuster](#): > > [https://www.washingtonpost.com/news/energy-environment/wp/2016/12/22/the-coming-battle-between-the-trump-team-and-economists-over-the-true-cost-of-climate-change/](https://www.washingtonpost.com/news/energy-environment/wp/2016/12/22/the-coming-battle-between-the-trump-team-and-economists-over-the-true-cost-of-climate-change/) > > More recent economical studies do show a lot of lost opportunities if we continue in the same path or a worst one as Trump and minions want. > > [Climate Change and Economic Production by Country](http://web.stanford.edu/~mburke/climate/) You’ve provided some links that themselves give a number of links … is there a specific paper in there you wish to discuss? I did gloss through [“Global non-linear effect of temperature on economic production”](http://web.stanford.edu/~mburke/climate/BurkeHsiangMiguel2015.pdf) … to know what the economy in the USA will be like with +5ºC we need only look today at places that are already +5ºC … pretty much all impoverished third-world nations … thus the economy in the USA will be as an impoverished third-world nation … Canada will be the new United States … we’ll have to migrate … ---
**Author:** ![squidfood](https://avatars.discourse-cdn.com/v4/letter/s/a87d85/32.png) [@squidfood](https://boards.straightdope.com/u/squidfood)\ **Post date:** [February 22, 2017, 8:34pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/53 "2017-02-22T20:34:35Z")
> [@watchwolf49](#): > > I did gloss through [“Global non-linear effect of temperature on economic production”](http://web.stanford.edu/~mburke/climate/BurkeHsiangMiguel2015.pdf) … to know what the economy in the USA will be like with +5ºC we need only look today at places that are already +5ºC … pretty much all impoverished third-world nations … thus the economy in the USA will be as an impoverished third-world nation … > > Canada will be the new United States … we’ll have to migrate … This study seems to be driven _hugely_ by a correlation implies causation mentality. There are many reasons that the “cooler” countries of U.S., Europe and China are better developed and command more resources. These may have some historical roots in climate (in a Guns, Germs and Steel kind of way) but there’s no reason to believe those commanding positions would be “lost” by moving us out of some kind of ideal thermal envelope. I’m guessing it would be pretty easy to falsify this one, for example, by looking at it within the U.S. for all 50 states. Hmm. Ok, I just got [average annual temperatures](https://www.currentresults.com/Weather/US/average-annual-state-temperatures.php) and [GDP by state](https://en.wikipedia.org/wiki/List_of_U.S._states_by_GDP_per_capita). There’s one cold place with high GDP - Alaska, land of oil where they pay for you to live there. Otherwise, no trend whatsoever. Edit: sorry, there was a slight and noisy trend even without AK, this time driven at the other end by Mississippi. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [February 22, 2017, 9:57pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/54 "2017-02-22T21:57:42Z")
> [@squidfood](#): > > I’m guessing it would be pretty easy to falsify this one, for example, by looking at it within the U.S. for all 50 states. Hmm. > > Ok, I just got [average annual temperatures](https://www.currentresults.com/Weather/US/average-annual-state-temperatures.php) and [GDP by state](https://en.wikipedia.org/wiki/List_of_U.S._states_by_GDP_per_capita). There’s one cold place with high GDP - Alaska, land of oil where they pay for you to live there. Otherwise, no trend whatsoever. Hmm, the paper actually makes the point that “warming raises productivity in cool countries” and there was a big increase in Alaska from 2012 to 2015. “warming harms productivity in countries with high average temperatures”. Anyhow, the effects that they are talking about are regarding what it is likely to happen in the future, not the past if we are not preparing. The problem right now is that several politicians and interest groups would like that we remain just the same… unprepared. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [February 22, 2017, 10:23pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/55 "2017-02-22T22:23:56Z")
> [@watchwolf49](#): > > I did gloss through [“Global non-linear effect of temperature on economic production”](http://web.stanford.edu/~mburke/climate/BurkeHsiangMiguel2015.pdf) … to know what the economy in the USA will be like with +5ºC we need only look today at places that are already +5ºC … pretty much all impoverished third-world nations … thus the economy in the USA will be as an impoverished third-world nation … No, this is not the point of the study at all. You are even missing the graphs, North America is likely to get a diminished economy by 2100, but not as bad as many other nations. (And again, this is provided that no preparations or more emission controls are made, very likely considering the caliber of the current Republican leaders.) ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 22, 2017, 11:30pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/56 "2017-02-22T23:30:08Z")
> [@GIGObuster](#): > > No, this is not the point of the study at all. You are even missing the graphs, North America is likely to get a diminished economy by 2100, but not as bad as many other nations. (And again, this is provided that no preparations or more emission controls are made, very likely considering the caliber of the current Republican leaders.) > [@](#): > > Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Which graph are you looking at? … Figure 4a shows GDP per capita in Canada as doubling by 2100 … ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [February 22, 2017, 11:41pm UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/57 "2017-02-22T23:41:23Z")
The “business as usual” emissions scenario is a recipe for full-blown catastrophe. A few of the impacts [are shown here](https://www.ipcc.ch/publications_and_data/ar4/wg2/en/fig/figure-spm-2-l.png) and one can see the increasing severity as the temperature rise approaches 5°C. “Business as usual” emissions – the Republican program of denial and ignoring the problem – would take us beyond a catastrophically dangerous 8°C rise by 2150, and in point of fact we are very likely already committed to least a 5°C rise because of the time it will take to achieve emissions reductions and the lag of temperature behind the emissions forcings. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [February 23, 2017, 12:18am UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/58 "2017-02-23T00:18:50Z")
> [@wolfpup](#): > > Just a few points to keep the record straight. There are actually a whole host of different radiative forcings affecting the climate, mostly positive, some negative. [This is a fairly good graphical summary of the main ones](http://www.realclimate.org/images/ipcc_rad_forc_ar5.jpg). I think we are talking past each other a bit. My estimate that CO2 was responsible for about a third of the forcing is in reference to your statement that “The driving force between a mile-thick continental ice sheet and a hospitable temperate climate is the approximately 100 ppm of CO2 that separates glacial minima from interglacial maxima.” I.e., it applied to the forcing during the last glacial maximum relative to the interglacial period (pre-industrial). This is an estimate due to James Hansen. The chart you reference above is for the current forcings relative to the pre-industrial era. Here, CO2 clearly plays a larger role … In fact, the best estimate is that it is roughly 3/4 of the net forcing, but with big error bars. It could even be over 100% of the net forcing…i.e., the other forcings could total slightly negative. The big error bars are due mainly the the large uncertainty in the forcing due to aerosols. > [@](#): > > You mention albedo changes due to ice sheets and vegetation. It’s important to note that albedo changes are in two distinct categories: forcings and feedbacks, and need to be kept separate because they’re fundamentally different. An albedo forcing is an independent factor that drives the climate in and of itself – the primary example is land use and land cover changes from human activity, which you’ll find in the above chart. Ice cover changes, however, are feedbacks that are a direct consequence of Arctic warming and which amplify that warming when ice cover is reduced. They’re like the increase in water vapor that amplifies CO2 warming. Because they’re feedbacks intrinsically tied to the underlying forcings, these things don’t appear on the chart, but they’re obviously of critical importance in computing and modeling how climate responds to forcings. Right…The confusing thing though is that while it makes sense to consider such albedo changes (e.g., due to changes in ice cover) as feedbacks in the current situation, where the forcing is the changes in greenhouse gas concentrations (and other things like aerosols) that we are making, it is reasonable to think of them as forcings when one looks at the change from the last glacial maximum to the interglacial. The whole distinction between what one considers a forcing and a feedback and in what context gets a little dicey and leads into discussions of the different kinds of climate sensitivity one can usefully define, such as the Charney sensitivity vs. the Earth system sensitivity (discussed to some degree here: [RealClimate: On sensitivity: Part I](http://www.realclimate.org/index.php/archives/2013/01/on-sensitivity-part-i/) ) ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [February 23, 2017, 12:35am UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/59 "2017-02-23T00:35:27Z")
> [@watchwolf49](#): > > Which graph are you looking at? … Figure 4a shows GDP per capita in Canada as doubling by 2100 … Figure 4 b, North America. And really, North America is also the USA and Mexico. Look it up. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 23, 2017, 1:24am UTC](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246/60 "2017-02-23T01:24:09Z")
> [@wolfpup](#): > > The “business as usual” emissions scenario is a recipe for full-blown catastrophe. A few of the impacts [are shown here](https://www.ipcc.ch/publications_and_data/ar4/wg2/en/fig/figure-spm-2-l.png) and one can see the increasing severity as the temperature rise approaches 5°C. “Business as usual” emissions – the Republican program of denial and ignoring the problem – would take us beyond a catastrophically dangerous 8°C rise by 2150, and in point of fact we are very likely already committed to least a 5°C rise because of the time it will take to achieve emissions reductions and the lag of temperature behind the emissions forcings. Do you mean “business as usual” in the next 125 years to be the same as the last 125 years … when we had no powered flight, state-of-the-art electronics was the incandescent light bulb, and the closest thing to the internet was countries color-coding their postage stamps so all the other countries would have an idea of their cost? … or do you mean “business-as-usual” to mean spectacular technological development in all areas of human activities that we’ve seen these past 125 years? … The United States is fond of alternating between liberal and conservative governments … two steps forward and one step back; it’s the American Way™ !!! … and remember, the corporate tax rollback will make solar panels cheaper as well … Do you have a link to the math that came up with the +8ºC number? … [Previous page](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246.md?page=2) [Next page](https://boards.straightdope.com/t/the-defect-in-the-climate-has-always-changed-argument/780246.md?page=4)