I agree completely with your post inasmuch as your doing a good job presenting the big picture and most of the science in the issue.
I have a small problem with a couple of the statements you made, namely "CFCs do not cause global warming" and "Ozone depletion is not important... in global warming". CFCs are actually a reasonably potent greenhouse gas (100 year global warming potential of several thousand), as are many of the CFC replacements (HFCs). They still rank well below CO2, CH4, and N2O in terms of total anthropogenic contribution because not that much of them is emitted, but good climate models include them (especially since HFC emissions may rise in the future).
Ozone also serves as a greenhouse gas: stratospheric ozone depletion, therefore, may actually serve as a global cooling mechanism. In fact, one hypothesis for why the interior of Antartica has cooled is that ozone depletion, combined with a strong polar vortex, has negated the temperature rise that climate models otherwise predict at extreme latitudes...
Anyway, good post, but I thought you might like to hear the nitpicking details anyway.
Um. If you read the literature on global warming, you will note that the majority (about 70%) of the 25 cm to 1 m predicted sea level rise in the next century is due to _thermal expansion_, not snow melt.
(see Webster et al., Climatic Change, 61(3): 295-320, 2003 or any other reputable paper on climate change that predicts sea level rise)
For the last decade or so, the global warming community has assumed that the increased melting at the edges of Antartica + Greenland will be approximately offset by the increases of precipitation in the center of the masses - in the near term.
In the several century+ term, yes, then we might worry about major ice shelf collapse.
On the issue of central Antartic cooling: some researchers suggest it is due to the combination of the ozone hole and the southern vortex (I don't remember the citation right now).
-Marcus
So I remember reading a few years ago that there was a slight asymmetry in chirality of amino acids found in asteroids - anyone know if more data has been found? Or theories on _why_ there would be this asymmetry?
I seem to remember that some famous physicist was quoted when they discovered an asymmetry due to the weak nuclear force in (muon?) decay that "God is not left-handed!" (similar to "God does not play dice").
But apparently, God plays dice left-handedly. =)
-Marcus
(Note that with amino acids, biological mechanisms explain the massive predominance that we observe, and one could certainly assume that even a universe which had no bias at all that biology would tip the balance on any given life-bearing planet one way or the other - the interesting question is if there is an inherent bias towards left-handed amino acids or if it was just a 50% chance stochastic choice)
Um. So, a dyed-in-the-wool moderate takes a position that is at one end of the distribution of all the scientists who work in the field? I assert that you are nowhere near the middle of this argument. Anymore than intelligent design advocates are the "moderate" side in the evolution vs. creationism debate.
The vast majority of the models out there agree with the "emissions folk" (here I include, in no particular order, the GFDL labs, the PNNL labs, Wigley et al, the AGU, the MIT Joint Program on Climate Change, NOAA, the NAS, the IPCC, Schneider et al, the Hadley Center, etc. etc.). The "no impact" folk on the other hand - Christy, Lindzen, Baliunas, Singer - are a real minority.
I said that _if_ "you are sticking by your '1/10th of 1 percent' would make big changes" _then_ you would have to admit that we are making huge changes. Or are you saying that the sun changing by 1/10th of 1 percent is significant, but humans changing its effective radiation by 1 percent is small? Or are you saying that humans haven't effected the radiation budget of the earth?
It is quite likely that humans are responsible for much of the last several decades of warming. There have been plenty of attribution studies attribution studies that have shown this statistically. More to the point, if we maintain a business-as-usual path, we are very likely to radically warm the earth over the coming centuries. We can't stop change from happening, but we can take actions that would reduce the rate of the change that we are causing. And yes, we need to balance the costs of emissions controls against the expected value of the environmental benefits we will receive - I believe that economic growth is vital to improving the health, happiness, and well-being of humans, but not without regulation.
The yahoos who keep going on about not doing anything to reduce emissions until we are absolutely certain about its impact are ignoring the fact that decisions are made under uncertainty all the time. There is certainly enough evidence that we are impacting the earth's climate, and enough basic scientific understanding to know that we will continue to do so, and enough economics understanding to be able to make some guesses about what the right balance of controls are, that we should be at least implementing starter policies (not necessarily Kyoto - I'd prefer a carbon tax, and real scientific investments into fusion and zero-carbon technologies)
Or we can stick our fingers in our ears and chant mindlessly that "its not happening" and "its not our fault" because, after all, this is a long term problem and who cares if future generations curse us for our short sightedness?
There is a chance that you are right, maybe we'll luck out, maybe the climate sensitivity will be at the low end of the model results. Are you willing to take the greenhouse gamble for the next generation? I prefer to take the optimal path given our level of understanding rather than saying "maybe nothing will happen so let's do nothing".
And people die all the time. So why stop wars? We'll just make more people later.
For a worst case scenario, you can go to that Pentagon report - http://www.ems.org/climate/pentagon_climatechange. pdf - and read up.
Note that that report is _not_ a prediction of anything likely to happen, it wasn't even written by real climate scientists, but it is the sort of worst, worst case one might imagine.
The likely bad cases are increases in sea level of a meter in the next century causing mass migrations from Bangladesh and other low-lying areas and billions of storm damage even in the US, changes in rainfall patterns causing droughts and flooding (possibly sometimes in the same place!) and generally causing agricultural producers a lot of pain (especially in the developing world where they don't always have irrigation or the ability to change crops easily as the environment changes), thawing of the permafrost leading to collapsing of infrastructure in Alaska and Russia, increased/changed storm patterns (hurricanes, tornadoes)... shall I go on? Yes, humanity will survive, but maybe its worth doing a little something now to reduce the chances of these worst cases.
Your link talks about 0.05% increases in solar radiation per decade. Radiative forcing increases due to GHGs are nearly 1% over the last two centuries. Even if the sun has been steadily increasing at the 0.05% rate for 2 centuries, the two trends would be of comparable magnitude - and the human one is accelerating.
The Sun may be big, but without the magnifying glass it isn't likely to fry the ant...
Actually, we have a lot of data. We would like more, but we have to make do with what we have.
And our data allows us to look at atmospheric concentrations accurately back 400,000 years (Vostok ice core), global average temperatures back 100 years (thermoeters, both measuring air and surface water temperatures, reasonably accurate), proxy global average temperatures back 1000 years (with significant uncertainties), and all sorts of other data. Some of it going back millions of years.
Plus understanding of basic physics. Undoubted human induced increases in GHG concentrations undoubtably increase the radiative forcing at the earth's surface, which undoubtably will lead to some warming. The question is how much. Our best guesses vary from 1 degrees to 5 degrees celcius over the next century... the upper end of that range will be pretty uncomfortable.
btw, _all_ models predict that the earth will be warming up over the next century. The majority of the ones that claim a new ice do so by predicting a collapse of the thermohaline circulation - brought on by earlier warming.
There is still uncertainty involved, but it is a lot more than just "speculation"
Given that we receive about 340 W/m2 of solar radiation, and given that the forcing due to human induced greenhouse gas emissions is _already_ 2.4 W/m2 and even if we stabilize CO2 concentrations at 550 ppm it will rise _another_ 3 W/m2, we are going to be effectively adding 1.5% or more to solar luminosity. (Yes, there is some cooling effect due to aerosol emissions, but aerosols are a flow pollutants, GHGs are a stock, which means that the aerosol influence won't grow the same way).
So if you are sticking by your "1/10th of 1 percent" would make big changes, then you have to admit that we're making HUGE changes.
Um. We have much more than correlational data. We have something called science. Look up Svante Arrhenius and Tyndall - they were around 100 years ago, they figured out that CO2 could absorb heat, and Svante was even clever enough to predict that if we put enough of it into the atmosphere, we might warm up the planet.
While the climate system is complicated, it is pretty obvious to any knowledgeable person that if you increase the radiative forcing at the surface by several watts/meter squared, that the likely outcome is that the temperature will rise - and when the temperature does rise in correspondence with theory, that is much more convincing than just saying "CO2 and temperature rose at the same time and therefore there is causation".
This doesn't say that all the warming is caused by humans, but some of it is. And some pretty smart people do relatively sophisticated studies to try and determine the proportions more precisely - look up "climate attribution".
There's still uncertainty, but good policymakers should know that they can act even when uncertainty exists. I'd say we have much better evidence for human induced climate change than for WMDs in Iraq, for example...
Um. Anti-ozone pollution is _not_ the cause of global warming. Actually, ironically enough, it is the opposite - the ozone hole over the antarctic is one of the reasons that the antarctic has _not_ warmed much over the last 30 years.
Anyway, yes, there is natural variability. But humans have dumped enough GHGs into the atmosphere that our contribution is an order of magnitude larger than the sun's variation over the last 250 years. http://www.ipcc.ch/pub/spm22-01.pdf page 8, for a reference.
Finally, some people have proposed putting sunshades in orbit or the equivalent, but it seems like it first we can try to reduce our contribution by controlling some of our emissions.
What uncadonna said. Basically, each CO2 molecule acts to trap heat over its 100+ year average lifetime in the atmosphere. The heat generated by the combustion that released the CO2 is miniscule in comparison.
In a correction to uncadonna, I will note that my understanding of the urban heat island effect was that it was in large part due to changes in albedo of urban areas, and not direct heat. (ie, a lot of black road surfaces and dark rooftops) In fact, some global warming proposals include measures like painting all the rooftops in the South (in the US) white to reduce demand on air conditioning by making those cities cooler...
The short answer is that global warming leads to increased evaporation. Increased evaporation leads to increased precipitation. Moreover, increased air temperatures mean that any given parcel of air can hold more water before reaching the point at which the water will condense out, which means that the precipitation events (when they happen) are likely to be more intense. All of which leads to more flooding (of course, coastal areas will see more flooding due to sea level rise from thermal expansion of the ocean plus glacial melt)
Having said that, regional predictions from climate models are highly, highly uncertain.
Of the viewpoints you listed, only 1 of them has reached any sort of international consensus. That is the viewpoint that humanity has been significantly changing the radiative balance of the atmosphere (with a net increase), and that climate change will result. Climate change includes (but is not limited to) an increase in global mean surface temperatures in the short and medium terms, and probably the long (multiple century) term too failing some non-linear event like thermohaline circulation collapse.
Check out wikipedia's article on global cooling if you want to see the real story about this so-called "global-cooling scare" that the Global Climate Coalition and other skeptics groups like harping on.
http://en.wikipedia.org/wiki/Global_cooling
Christy & co. (your "nothing" link) are a real minority in the global climate community, and the only reason anyone ever hears about them is because industry looks for any dissent at all to publicize (like intelligent design people looking for the outlier biology professor to talk against evolution).
And I think you are exaggerating the air pollution results too: yes, there are significant health effects from particulates and ozone (which are in part visible because we've improved health in other areas so much that we have increased lifespans during which to get cancers, and our infant mortality rates have dropped such that baby deaths from air pollution are now a visible percentage of the whole), but we'll still be able to breathe.
Maybe if you tried some non-elementary-school science you would get some better results.
For example, try this on for size: we know (100% sure) that increases in CO2 concentration in the atmosphere are human induced. We know (100% sure) that those increases will lead to a direct radiative forcing increase of 1.5 W/m2 (and growing fast). We know that then total solar radiation is 340 W/m2. Therefore, we have, just from CO2 emissions, effectively made the sun 0.5% brighter. Add all the other GHGs in, and we're at 1%. And by the end of the century, we're likely to hit 2% or more. I think making the sun 2% brighter is pretty darn significant, especially given the possibility of positive feedback loops.
Will civilization end? No. But a lot of the climate changes that will occur due to increased radiative forcing will be painful for humanity. More painful than the measures we could take to reduce emissions.
So take some good Earth, Atmosphere and Planetary science classes, and perhaps some economics and politics classes while you are at it, and if you want some additional biology classes (so you can learn about the difference in reactions of C3 vs. C4 plants to increased CO2 levels, etc.), and then come back and post again.
1) The measured increase of the Solar radiation over the last 250 years has been about half a watt per meter squared. The increase in radiative forcing due to the change in carbon dioxide concentrations in the atmosphere is about 1.5 W/m2. See http://www.ipcc.ch/pub/spm22-01.pdf page 8 for a graphical representation of different forcings and the level of understanding of each. (For comparison, total solar radiation is 340 W/m2, and some models project that human induced radiative forcing change will increase from a couple W/m2 now to 7 W/m2 or more by 2100 - which would be like increasing the Sun's output by 2%. Which is kind of disturbingly large.)
2) Ok. So the Earth survived warmer and colder temperatures in the past. Does that mean it will be comfortable for us to live through the transition to those new states? Not really.
3) Um. CFC's in the environment are 100% human made. If you are talking about GHGs, the vast majority of the _change_ in the last thousand years is human activity related (bovine methane emissions I count as human activity related, as are rice paddy methane emissions). The occasional volcano like Pinatubo that manages to spew aerosols into the stratosphere can induce a year or two of measurable global cooling. However, you will note that even Pinatubo wasn't enough to prevent the 1990s from having record high global average temperatures.
And see above: several percent increase in the sun's effective output due to human influence. If there are any positive feedback loops (like retreating glaciers decreasing the earth's albedo, or increased evaporation increasing the GHG content of the atmosphere), then we can really make a difference... in a bad way (for us).
It is a tricky balance to see how much we can reduce GHG emissions without killing economies, but we can do at least _some_ reductions...
It certainly has precedent. Look up methyl bromide and golf course and the Montreal Protocol. Apparently, under this administration, golf courses are a "critical use", more important than saving the ozone hole or anything else.
I actually don't mind people spending their brainpower and research money on sort of useless projects like making golf courses greener - what I do mind is people taking environmental risks on these useless projects.
Actually, I believe the permit program sells permits for 1 ton of emissions in a given year. Though you are allowed to "bank" emissions, such that if you emit less than your permits, you can roll that over into next year (to give incentives to people to start cleaning up earlier, and to reduce the pain of the transition between stage 1 and the significantly stricter stage 2 of the SO2 program. There are some nice graphs out there showing how the step function of the governmental program was nicely smoothed through the banking program. See Ellerman, et al., "Markets for Clean Air" for a good book on the subject.).
But it is not "1 ton per year for perpetuity".
On the other hand, permit _allocation_ is sometimes done that way: a coal plant will be assigned X number of permits every year, often based on "grandfathered" emissions. But we won't get into allocation issues in this post...
Actually, methane on earth has a half-life of 10 to 15 years - mostly due to oxidation by the hydroxyl radical. I think the "300 years" number actually does refer to the theoretical lifetime of methane on Mars (the uv intensity would be much larger on Mars than on Earth because the lack of ozone layer would more than make up for the increased distance to the sun, but the photochemical process would still be much slower than the chemical process here)
If you go to the
original study you can see that it is in fact well-caveated. It was a hypothetical scenario - designed to look at unlikely and extreme outliers of what climate scientists are studying.
Note that I am a believer in reducing greenhouse gas emissions in order to reduce the likelihood of extreme negative climate change events. However, the Pentagon report should really not be used as an example of mainstream climate science (I believe the authors themselves do not work in the field). And the Guardian really went overboard in their reporting of it.
Subject: G7) Why doesn't the South Atlantic Ocean experience tropical cyclones?
Though many people might speculate that the sea surface temperatures are too cold, the primary reasons that the South Atlantic Ocean gets no tropical cyclones are that the tropospheric (near surface to 200mb) vertical wind shear is much too strong and there is typically no inter-tropical convergence zone (ITCZ) over the ocean (Gray 1968). Without an ITCZ to provide synoptic vorticity and convergence (i.e. large scale spin and thunderstorm activity) as well as having strong wind shear, it becomes very difficult to nearly impossible to have genesis of tropical cyclones.
However, in rare occasions it may be possible to have tropical cyclones form in the South Atlantic. In McAdie and Rappaport (1991), the US National Hurricane Center documented the occurrence of a strong tropical depression/weak tropical storm that formed off the coast of Congo in mid-April 1991. The storm lasted about five days and drifted toward the west-southwest into the central South Atlantic. So far, there has not been a systematic study as to the conditions that accompanied this rare event.
In fact, those of us who do climate science use the term "climate change" rather than "global warming". As MrWa stated, thermohaline circulation (gulf stream) collapse would lead to anomalous cooling in the northern Atlantic (unlikely in the near term according to the models I've seen), but we also study aerosol effects (sulfate cooling, the effect of the Pinatubo eruption, etc), and so on. And in general regional changes in temperature, while hard to predict, can be either positive or negative even if global mean surface temperatures are increasing.
In any case, most models do not predict large warming of the equatorial band, partially because evaporation over tropical oceans keeps the atmosphere from heating. Of course, this increased evaporation leads to increased latent heat, which is a possible cause of extreme weather.
Having said that, one extreme event does not proof of climate change make. Climate change is about long term trends, not short term weather. If we see more South Atlantic hurricanes over the next decade, then there would be an indication that they could be a result of climate change.
Then we could look for the proximate cause: increased latent heat, ocean temperature patterns, change in winds, salinity changes, all of the above concurrent or consecutive, whatever. Then we would ask, is this change something we would expect from human induced change, eg increased greenhouse gas forcing or aerosols or something else.
Actually, the the NOAA FAQ lists hurricane/cyclone terminology, and oddly there is no approved name for a South Atlantic hurricane... which may testify further to the rareness of the event. Quote follows:
Tropical cyclones with maximum sustained surface winds of less than 17 m/s (34 kt, 39 mph) are called "tropical depressions". (This is not to be confused with the condition mid-latitude people get during a long, cold and grey winter wishing they could be closer to the equator;-)) Once the tropical cyclone reaches winds of at least 17 m/s they are typically called a "tropical storm" and assigned a name. If winds reach 33 m/s (64 kt, 74 mph)), then they are called: a "hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E); a "typhoon" (the Northwest Pacific Ocean west of the dateline); a "severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E); a "severe cyclonic storm" (the North Indian Ocean); and a "tropical cyclone" (the Southwest Indian Ocean) (Neumann 1993).
And if you read the article, you realize that NASA installed defective actuators not once, but twice! The first being the one that was successfully flown 30 times, and the second in the spare actuators.
Given the complexity of a system like the shuttle, it is not surprising that out of 1000s of components there could be a mistake in one of them (and given some redundancy and robustness, it is not surprising that the shuttle could fly 30 times with one or more poorly installed components, though one would not normally want to bet on that...).
However, two errors out of 8 actuators checked implies some serious quality control issues.
Um. I _did_ mention size being an important characteristic of these particles, did I not? Sea spray particles are relatively large, I believe and not a major contributor to PM2.5. I'm not sure, but I could also believe that soluble small particles might have less impact than insoluble ones (assuming that the impact is due to irritation, and not a toxic organic compound).
I happen to like some amount of regulation. Leaded gasoline, thalidomide, CFCs, DDT, tobacco, asbestos, car exhaust... the list of substances that were found to be toxic after they entered widespread use is not insignificant. I don't advocate "ban everything new", but I do think that some measure of caution when introducing something that has a sufficiently different profile (size, shape, chemical structure) from existing products and may become widely used (we _are_ hoping that nanoparticles are useful enough to appear in many applications, right?) should merit at least a few years of serious investigation into its impacts. And then you balance the potential damage it can do with the potential benefits and make your best _informed_ decision.
As an environmental economics instructor once said: "A no-tolerance policy towards a lot of risks would lead us to lock ourselves up in a room all day (which itself is not riskless, because the roof could fall over your head)."
However, I am not advocating "no-tolerance" but rather "thorough examination" - which I will grant means different things to different people.
-Marcus, hoping that nanotech will be one of the major technologies of the future, but still wanting to be cautious about it.
Slashdot Mirror
I agree completely with your post inasmuch as your doing a good job presenting the big picture and most of the science in the issue.
I have a small problem with a couple of the statements you made, namely "CFCs do not cause global warming" and "Ozone depletion is not important... in global warming". CFCs are actually a reasonably potent greenhouse gas (100 year global warming potential of several thousand), as are many of the CFC replacements (HFCs). They still rank well below CO2, CH4, and N2O in terms of total anthropogenic contribution because not that much of them is emitted, but good climate models include them (especially since HFC emissions may rise in the future).
Ozone also serves as a greenhouse gas: stratospheric ozone depletion, therefore, may actually serve as a global cooling mechanism. In fact, one hypothesis for why the interior of Antartica has cooled is that ozone depletion, combined with a strong polar vortex, has negated the temperature rise that climate models otherwise predict at extreme latitudes...
Anyway, good post, but I thought you might like to hear the nitpicking details anyway.
Um. If you read the literature on global warming, you will note that the majority (about 70%) of the 25 cm to 1 m predicted sea level rise in the next century is due to _thermal expansion_, not snow melt. (see Webster et al., Climatic Change, 61(3): 295-320, 2003 or any other reputable paper on climate change that predicts sea level rise) For the last decade or so, the global warming community has assumed that the increased melting at the edges of Antartica + Greenland will be approximately offset by the increases of precipitation in the center of the masses - in the near term. In the several century+ term, yes, then we might worry about major ice shelf collapse. On the issue of central Antartic cooling: some researchers suggest it is due to the combination of the ozone hole and the southern vortex (I don't remember the citation right now). -Marcus
So I remember reading a few years ago that there was a slight asymmetry in chirality of amino acids found in asteroids - anyone know if more data has been found? Or theories on _why_ there would be this asymmetry?
I seem to remember that some famous physicist was quoted when they discovered an asymmetry due to the weak nuclear force in (muon?) decay that "God is not left-handed!" (similar to "God does not play dice").
But apparently, God plays dice left-handedly. =)
-Marcus
(Note that with amino acids, biological mechanisms explain the massive predominance that we observe, and one could certainly assume that even a universe which had no bias at all that biology would tip the balance on any given life-bearing planet one way or the other - the interesting question is if there is an inherent bias towards left-handed amino acids or if it was just a 50% chance stochastic choice)
The vast majority of the models out there agree with the "emissions folk" (here I include, in no particular order, the GFDL labs, the PNNL labs, Wigley et al, the AGU, the MIT Joint Program on Climate Change, NOAA, the NAS, the IPCC, Schneider et al, the Hadley Center, etc. etc.). The "no impact" folk on the other hand - Christy, Lindzen, Baliunas, Singer - are a real minority.
I said that _if_ "you are sticking by your '1/10th of 1 percent' would make big changes" _then_ you would have to admit that we are making huge changes. Or are you saying that the sun changing by 1/10th of 1 percent is significant, but humans changing its effective radiation by 1 percent is small? Or are you saying that humans haven't effected the radiation budget of the earth?
It is quite likely that humans are responsible for much of the last several decades of warming. There have been plenty of attribution studies attribution studies that have shown this statistically. More to the point, if we maintain a business-as-usual path, we are very likely to radically warm the earth over the coming centuries. We can't stop change from happening, but we can take actions that would reduce the rate of the change that we are causing. And yes, we need to balance the costs of emissions controls against the expected value of the environmental benefits we will receive - I believe that economic growth is vital to improving the health, happiness, and well-being of humans, but not without regulation.
The yahoos who keep going on about not doing anything to reduce emissions until we are absolutely certain about its impact are ignoring the fact that decisions are made under uncertainty all the time. There is certainly enough evidence that we are impacting the earth's climate, and enough basic scientific understanding to know that we will continue to do so, and enough economics understanding to be able to make some guesses about what the right balance of controls are, that we should be at least implementing starter policies (not necessarily Kyoto - I'd prefer a carbon tax, and real scientific investments into fusion and zero-carbon technologies)
Or we can stick our fingers in our ears and chant mindlessly that "its not happening" and "its not our fault" because, after all, this is a long term problem and who cares if future generations curse us for our short sightedness?
There is a chance that you are right, maybe we'll luck out, maybe the climate sensitivity will be at the low end of the model results. Are you willing to take the greenhouse gamble for the next generation? I prefer to take the optimal path given our level of understanding rather than saying "maybe nothing will happen so let's do nothing".
-Marcus
And people die all the time. So why stop wars? We'll just make more people later.
. pdf - and read up.
For a worst case scenario, you can go to that Pentagon report - http://www.ems.org/climate/pentagon_climatechange
Note that that report is _not_ a prediction of anything likely to happen, it wasn't even written by real climate scientists, but it is the sort of worst, worst case one might imagine.
The likely bad cases are increases in sea level of a meter in the next century causing mass migrations from Bangladesh and other low-lying areas and billions of storm damage even in the US, changes in rainfall patterns causing droughts and flooding (possibly sometimes in the same place!) and generally causing agricultural producers a lot of pain (especially in the developing world where they don't always have irrigation or the ability to change crops easily as the environment changes), thawing of the permafrost leading to collapsing of infrastructure in Alaska and Russia, increased/changed storm patterns (hurricanes, tornadoes)... shall I go on? Yes, humanity will survive, but maybe its worth doing a little something now to reduce the chances of these worst cases.
Your link talks about 0.05% increases in solar radiation per decade. Radiative forcing increases due to GHGs are nearly 1% over the last two centuries. Even if the sun has been steadily increasing at the 0.05% rate for 2 centuries, the two trends would be of comparable magnitude - and the human one is accelerating.
The Sun may be big, but without the magnifying glass it isn't likely to fry the ant...
Actually, we have a lot of data. We would like more, but we have to make do with what we have.
And our data allows us to look at atmospheric concentrations accurately back 400,000 years (Vostok ice core), global average temperatures back 100 years (thermoeters, both measuring air and surface water temperatures, reasonably accurate), proxy global average temperatures back 1000 years (with significant uncertainties), and all sorts of other data. Some of it going back millions of years.
Plus understanding of basic physics. Undoubted human induced increases in GHG concentrations undoubtably increase the radiative forcing at the earth's surface, which undoubtably will lead to some warming. The question is how much. Our best guesses vary from 1 degrees to 5 degrees celcius over the next century... the upper end of that range will be pretty uncomfortable.
btw, _all_ models predict that the earth will be warming up over the next century. The majority of the ones that claim a new ice do so by predicting a collapse of the thermohaline circulation - brought on by earlier warming.
There is still uncertainty involved, but it is a lot more than just "speculation"
Given that we receive about 340 W/m2 of solar radiation, and given that the forcing due to human induced greenhouse gas emissions is _already_ 2.4 W/m2 and even if we stabilize CO2 concentrations at 550 ppm it will rise _another_ 3 W/m2, we are going to be effectively adding 1.5% or more to solar luminosity. (Yes, there is some cooling effect due to aerosol emissions, but aerosols are a flow pollutants, GHGs are a stock, which means that the aerosol influence won't grow the same way).
So if you are sticking by your "1/10th of 1 percent" would make big changes, then you have to admit that we're making HUGE changes.
Um. We have much more than correlational data. We have something called science. Look up Svante Arrhenius and Tyndall - they were around 100 years ago, they figured out that CO2 could absorb heat, and Svante was even clever enough to predict that if we put enough of it into the atmosphere, we might warm up the planet.
While the climate system is complicated, it is pretty obvious to any knowledgeable person that if you increase the radiative forcing at the surface by several watts/meter squared, that the likely outcome is that the temperature will rise - and when the temperature does rise in correspondence with theory, that is much more convincing than just saying "CO2 and temperature rose at the same time and therefore there is causation".
This doesn't say that all the warming is caused by humans, but some of it is. And some pretty smart people do relatively sophisticated studies to try and determine the proportions more precisely - look up "climate attribution".
There's still uncertainty, but good policymakers should know that they can act even when uncertainty exists. I'd say we have much better evidence for human induced climate change than for WMDs in Iraq, for example...
Um. Anti-ozone pollution is _not_ the cause of global warming. Actually, ironically enough, it is the opposite - the ozone hole over the antarctic is one of the reasons that the antarctic has _not_ warmed much over the last 30 years.
Anyway, yes, there is natural variability. But humans have dumped enough GHGs into the atmosphere that our contribution is an order of magnitude larger than the sun's variation over the last 250 years. http://www.ipcc.ch/pub/spm22-01.pdf page 8, for a reference.
Finally, some people have proposed putting sunshades in orbit or the equivalent, but it seems like it first we can try to reduce our contribution by controlling some of our emissions.
What uncadonna said. Basically, each CO2 molecule acts to trap heat over its 100+ year average lifetime in the atmosphere. The heat generated by the combustion that released the CO2 is miniscule in comparison.
In a correction to uncadonna, I will note that my understanding of the urban heat island effect was that it was in large part due to changes in albedo of urban areas, and not direct heat. (ie, a lot of black road surfaces and dark rooftops) In fact, some global warming proposals include measures like painting all the rooftops in the South (in the US) white to reduce demand on air conditioning by making those cities cooler...
The short answer is that global warming leads to increased evaporation. Increased evaporation leads to increased precipitation. Moreover, increased air temperatures mean that any given parcel of air can hold more water before reaching the point at which the water will condense out, which means that the precipitation events (when they happen) are likely to be more intense. All of which leads to more flooding (of course, coastal areas will see more flooding due to sea level rise from thermal expansion of the ocean plus glacial melt)
Having said that, regional predictions from climate models are highly, highly uncertain.
Of the viewpoints you listed, only 1 of them has reached any sort of international consensus. That is the viewpoint that humanity has been significantly changing the radiative balance of the atmosphere (with a net increase), and that climate change will result. Climate change includes (but is not limited to) an increase in global mean surface temperatures in the short and medium terms, and probably the long (multiple century) term too failing some non-linear event like thermohaline circulation collapse.
Check out wikipedia's article on global cooling if you want to see the real story about this so-called "global-cooling scare" that the Global Climate Coalition and other skeptics groups like harping on.
http://en.wikipedia.org/wiki/Global_cooling
Christy & co. (your "nothing" link) are a real minority in the global climate community, and the only reason anyone ever hears about them is because industry looks for any dissent at all to publicize (like intelligent design people looking for the outlier biology professor to talk against evolution).
And I think you are exaggerating the air pollution results too: yes, there are significant health effects from particulates and ozone (which are in part visible because we've improved health in other areas so much that we have increased lifespans during which to get cancers, and our infant mortality rates have dropped such that baby deaths from air pollution are now a visible percentage of the whole), but we'll still be able to breathe.
Maybe if you tried some non-elementary-school science you would get some better results.
For example, try this on for size: we know (100% sure) that increases in CO2 concentration in the atmosphere are human induced. We know (100% sure) that those increases will lead to a direct radiative forcing increase of 1.5 W/m2 (and growing fast). We know that then total solar radiation is 340 W/m2. Therefore, we have, just from CO2 emissions, effectively made the sun 0.5% brighter. Add all the other GHGs in, and we're at 1%. And by the end of the century, we're likely to hit 2% or more. I think making the sun 2% brighter is pretty darn significant, especially given the possibility of positive feedback loops.
Will civilization end? No. But a lot of the climate changes that will occur due to increased radiative forcing will be painful for humanity. More painful than the measures we could take to reduce emissions.
So take some good Earth, Atmosphere and Planetary science classes, and perhaps some economics and politics classes while you are at it, and if you want some additional biology classes (so you can learn about the difference in reactions of C3 vs. C4 plants to increased CO2 levels, etc.), and then come back and post again.
1) The measured increase of the Solar radiation over the last 250 years has been about half a watt per meter squared. The increase in radiative forcing due to the change in carbon dioxide concentrations in the atmosphere is about 1.5 W/m2. See http://www.ipcc.ch/pub/spm22-01.pdf page 8 for a graphical representation of different forcings and the level of understanding of each. (For comparison, total solar radiation is 340 W/m2, and some models project that human induced radiative forcing change will increase from a couple W/m2 now to 7 W/m2 or more by 2100 - which would be like increasing the Sun's output by 2%. Which is kind of disturbingly large.)
2) Ok. So the Earth survived warmer and colder temperatures in the past. Does that mean it will be comfortable for us to live through the transition to those new states? Not really.
3) Um. CFC's in the environment are 100% human made. If you are talking about GHGs, the vast majority of the _change_ in the last thousand years is human activity related (bovine methane emissions I count as human activity related, as are rice paddy methane emissions). The occasional volcano like Pinatubo that manages to spew aerosols into the stratosphere can induce a year or two of measurable global cooling. However, you will note that even Pinatubo wasn't enough to prevent the 1990s from having record high global average temperatures.
And see above: several percent increase in the sun's effective output due to human influence. If there are any positive feedback loops (like retreating glaciers decreasing the earth's albedo, or increased evaporation increasing the GHG content of the atmosphere), then we can really make a difference... in a bad way (for us).
It is a tricky balance to see how much we can reduce GHG emissions without killing economies, but we can do at least _some_ reductions...
It certainly has precedent. Look up methyl bromide and golf course and the Montreal Protocol. Apparently, under this administration, golf courses are a "critical use", more important than saving the ozone hole or anything else.
I actually don't mind people spending their brainpower and research money on sort of useless projects like making golf courses greener - what I do mind is people taking environmental risks on these useless projects.
Actually, I believe the permit program sells permits for 1 ton of emissions in a given year. Though you are allowed to "bank" emissions, such that if you emit less than your permits, you can roll that over into next year (to give incentives to people to start cleaning up earlier, and to reduce the pain of the transition between stage 1 and the significantly stricter stage 2 of the SO2 program. There are some nice graphs out there showing how the step function of the governmental program was nicely smoothed through the banking program. See Ellerman, et al., "Markets for Clean Air" for a good book on the subject.).
But it is not "1 ton per year for perpetuity".
On the other hand, permit _allocation_ is sometimes done that way: a coal plant will be assigned X number of permits every year, often based on "grandfathered" emissions. But we won't get into allocation issues in this post...
-Marcus
Actually, methane on earth has a half-life of 10 to 15 years - mostly due to oxidation by the hydroxyl radical. I think the "300 years" number actually does refer to the theoretical lifetime of methane on Mars (the uv intensity would be much larger on Mars than on Earth because the lack of ozone layer would more than make up for the increased distance to the sun, but the photochemical process would still be much slower than the chemical process here)
Note that I am a believer in reducing greenhouse gas emissions in order to reduce the likelihood of extreme negative climate change events. However, the Pentagon report should really not be used as an example of mainstream climate science (I believe the authors themselves do not work in the field). And the Guardian really went overboard in their reporting of it.
Subject: G7) Why doesn't the South Atlantic Ocean experience tropical cyclones?
Though many people might speculate that the sea surface temperatures are too cold, the primary reasons that the South Atlantic Ocean gets no tropical cyclones are that the tropospheric (near surface to 200mb) vertical wind shear is much too strong and there is typically no inter-tropical convergence zone (ITCZ) over the ocean (Gray 1968). Without an ITCZ to provide synoptic vorticity and convergence (i.e. large scale spin and thunderstorm activity) as well as having strong wind shear, it becomes very difficult to nearly impossible to have genesis of tropical cyclones.
However, in rare occasions it may be possible to have tropical cyclones form in the South Atlantic. In McAdie and Rappaport (1991), the US National Hurricane Center documented the occurrence of a strong tropical depression/weak tropical storm that formed off the coast of Congo in mid-April 1991. The storm lasted about five days and drifted toward the west-southwest into the central South Atlantic. So far, there has not been a systematic study as to the conditions that accompanied this rare event.
In any case, most models do not predict large warming of the equatorial band, partially because evaporation over tropical oceans keeps the atmosphere from heating. Of course, this increased evaporation leads to increased latent heat, which is a possible cause of extreme weather.
Having said that, one extreme event does not proof of climate change make. Climate change is about long term trends, not short term weather. If we see more South Atlantic hurricanes over the next decade, then there would be an indication that they could be a result of climate change.
Then we could look for the proximate cause: increased latent heat, ocean temperature patterns, change in winds, salinity changes, all of the above concurrent or consecutive, whatever. Then we would ask, is this change something we would expect from human induced change, eg increased greenhouse gas forcing or aerosols or something else.
Tropical cyclones with maximum sustained surface winds of less than 17 m/s (34 kt, 39 mph) are called "tropical depressions". (This is not to be confused with the condition mid-latitude people get during a long, cold and grey winter wishing they could be closer to the equator ;-)) Once the tropical cyclone reaches winds of at least 17 m/s they are typically called a "tropical storm" and assigned a name. If winds reach 33 m/s (64 kt, 74 mph)), then they are called: a "hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E); a "typhoon" (the Northwest Pacific Ocean west of the dateline); a "severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E); a "severe cyclonic storm" (the North Indian Ocean); and a "tropical cyclone" (the Southwest Indian Ocean) (Neumann 1993).
And if you read the article, you realize that NASA installed defective actuators not once, but twice! The first being the one that was successfully flown 30 times, and the second in the spare actuators.
Given the complexity of a system like the shuttle, it is not surprising that out of 1000s of components there could be a mistake in one of them (and given some redundancy and robustness, it is not surprising that the shuttle could fly 30 times with one or more poorly installed components, though one would not normally want to bet on that...).
However, two errors out of 8 actuators checked implies some serious quality control issues.
-Marcus
I happen to like some amount of regulation. Leaded gasoline, thalidomide, CFCs, DDT, tobacco, asbestos, car exhaust... the list of substances that were found to be toxic after they entered widespread use is not insignificant. I don't advocate "ban everything new", but I do think that some measure of caution when introducing something that has a sufficiently different profile (size, shape, chemical structure) from existing products and may become widely used (we _are_ hoping that nanoparticles are useful enough to appear in many applications, right?) should merit at least a few years of serious investigation into its impacts. And then you balance the potential damage it can do with the potential benefits and make your best _informed_ decision.
As an environmental economics instructor once said: "A no-tolerance policy towards a lot of risks would lead us to lock ourselves up in a room all day (which itself is not riskless, because the roof could fall over your head)." However, I am not advocating "no-tolerance" but rather "thorough examination" - which I will grant means different things to different people.
-Marcus, hoping that nanotech will be one of the major technologies of the future, but still wanting to be cautious about it.