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Clearing smog has led to 'global brightening'

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  • Clearing smog has led to 'global brightening'

    Fred Pearce, NewScientist.com - Full Article

    The efforts of industrialised nations to cut smog pollution has had a bizarre side-effect - accelerating global warming.

    New data show that after years of getting smoggier, our skies have become clearer since about 1990. And one effect has been to allow more solar radiation to reach the surface of the Earth.

    The phenomenon known as “global dimming” has gone into reverse, according to research by Martin Wild at the Institute for Atmospheric and Climate Science in Zurich, Switzerland, and been replaced by “global brightening” (Science. vol 308, p 847). “There is no longer a dimming to counteract the greenhouse effect,” he told New Scientist.

    Climate scientists say there have been two critical influences on global air temperatures in the past half-century. First, rising atmospheric concentrations of heat-trapping gases like carbon dioxide have warmed the Earth, by preventing more of the heat that reaches the Earth’s surface from escaping back into space.

    But a parallel increase in smog particles has shaded the planet, partly offsetting the warming. Past studies have shown an increase in average aerosol particle levels in the atmosphere between 1960 and 1990 that were sufficient to reduce solar radiation reaching the Earth’s surface by about 5%.

    The net effect of these two conflicting influences has been a warming of almost 0.5°C since 1960. But the rising levels of aerosols have led to concern that they might be masking greater underlying warming. And now the mask appears to be coming off.
    “And, remember: there's no 'I' in 'irony'” ~ Merlin Mann

  • #2
    Revenge of the Junk Belt theory! Creates quite the catch-22 doesn't it?
    “Inside every sane person there’s a madman struggling to get out”
    –The Light Fantastic, Terry Pratchett

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    • #3
      if true this will quickly shed light on trends. Now as as long as no one uses this as an excuse to bring smog back
      Wikipedia and Google.... the needles to my tangent habit.
      ________________________________________________

      That special feeling we get in the cockles of our hearts, Or maybe below the cockles, Maybe in the sub-cockle area, Maybe in the liver, Maybe in the kidneys, Maybe even in the colon, We don't know.

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      • #4
        In a round-about way, it reminds me of the shield plot-line in the second Highlander movie, but only in that it makes me wonder what we might do to combat this 'new' development.

        Waiting for the aliens
        “And, remember: there's no 'I' in 'irony'” ~ Merlin Mann

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        • #5
          second highlander movie, there was no second highlander movie, there was only the first, a mental blank and then the third
          Juu nin to iro


          English doesn't borrow from other languages. It follows them down dark alleys, knocks them over, and goes through their pockets for loose grammar.

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          • #6
            The erasing of my memory core must have failed
            “And, remember: there's no 'I' in 'irony'” ~ Merlin Mann

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            • #7
              There was a horizon program on BBC about this about 6 months ago. Afaik the information this is based on was from september 11th when the flights were cancelled. And there was a temperature rise due to the reduced amount of jet stream particles over those days.
              ______________________________
              Nothing is impossible, some things are just unlikely.

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              • #8
                Not saying you're entirely wrong, just find it hard to believe they would base all this on one particular day, as opposed to a random sampling over a given period. Then again, less intelligent things have happened before in this regard...
                “And, remember: there's no 'I' in 'irony'” ~ Merlin Mann

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                • #9


                  There is a transcript there too.



                  Maybe the new scientist used different information.
                  ______________________________
                  Nothing is impossible, some things are just unlikely.

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                  • #10
                    Reading over those links, they don't seem to negate the findings found in the article I posted; instead covering another aspect. I could be missing a key point that says otherwise, and this is not a topic of which I'm well versed.
                    “And, remember: there's no 'I' in 'irony'” ~ Merlin Mann

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                    • #11
                      I doubt very much whether there could ever be a reliable modelling of the effect for the following reasons:

                      1. Most atmospheric particulate aerosols are from natural causes (volcanos, sandstorms etc.)

                      2. Most aerosols are densest close under the tropopause, which is well away from smog layers.

                      3. There are two kinds of smog: winter smog is caused by emitting carbon particles from uncontrolled combustion of dirty fuel, notably coal, and these form condensation nuclei under rare weather conditions (cf. London smog in the 1950s). The other is a much more common effect and is a photochemical reaction between NOx and HCs, producing tropospheric ozone. This is the terrible smog found in many tropical cities, due to emissions from the combustion of mostly fossil fuels. It is also common in summer in many townships (cf LA, June to Nov.) and, in its least virulent form, is often referred to as a summer heat haze. Note that it is often of natural origin, with trees providing the HCs in the form of terpenes and terpenoids (cf Blue Mountains in NSW, rich in aromatic gum trees) and NOxs from forest fires, lightning, emissions from the sea etc. It is estimated that man-made pollutants are globally responsible for much less than half of photochemical smog.

                      4. As smog decomposes, the photochemical energy absorbed from the sun is released exothermically, so that it contributes to a temperature rise as well as global dimming.

                      5. The albedo of smog with carbon particle condensation is low, so that it is a toss-up whether there would be more or less radiative forcing from the smog itself or from the ground under the smog, were it not there.

                      6. The albedo of aerosols in the upper troposphere is also low and absorbs heat that warms the surrounding air, which is normally extremely cold (typically -50°C): this warmed air will be in the three convection cells in each hemisphere, so will reach the lower troposphere within days. However, the temp difference from this source will be very small, much less than a tenth of a degree.

                      7. Ozone-based smog levels have a very strong diurnal peak at about 1100 (in LA), dying off rapidly by 1400 to almost zero by 1800. This is because the smog itself prevents sufficient light from penetrating to the level of the sources of emissions to form more ozone, which has an atmospheric residence time of < 1 hour. The NOx emissions peak 1 to 2 hours earlier. The albedo is therefore very variable from one hour to the next.

                      8. The effects of temperature inversion stagnation and lofting are almost unpredictable and would be very difficult to model. In the case of temperature inversion, it would tend to form a "bubble" of hot air, until the temperature of the lower layers exceeded those retaining it, when it would burst. The effect of smog on this equation would be unpredictable.

                      IMHO, it would be a very courageous scientist who would make categorical statements about these effects, as there are far too many variables and insufficient dat to formulate a global model. I'm extremely sceptical about this kind of thing, with both positive and negative effects from a variety of causes. Dammit, we can't even forecast weather three days in advance at better than 70% accuracy and we have many of the world's supercomputers doing just that with the most advanced modelling. What hope is there to model such ephemeral effects accurately?
                      Brian (the devil incarnate)

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                      • #12
                        Which is why the US didn't trust said models and decided not to codify their likely incorrect assumptions into into treatties like Kyoto.

                        Dr. Mordrid
                        Dr. Mordrid
                        ----------------------------
                        An elephant is a mouse built to government specifications.

                        I carry a gun because I can't throw a rock 1,250 fps

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                        • #13
                          Originally posted by Dr Mordrid
                          Which is why the US didn't trust said models and decided not to codify their likely incorrect assumptions into into treatties like Kyoto.

                          Dr. Mordrid
                          That is something very different and very highly researched by hundreds of the leading atmospheric scientists throughout the world. The chart is already a few years old and illustrates a good correlation between global observations and the model, taking into account min and max variations. The 2008 IPCC report will feature an even more precise modelling with at least ten more parameters, with very little variation from the red line.

                          No serious atmospheric scientist today doubts the validity of anthropogenic climate change modelling and that it is a serious threat. What is worse that evidence is becoming available that there is a positive feedback loop that increased ice melt is releasing larger-than-anticipated greenhouse gases from clathrates, in turn raising temperatures causing more ice melt. The snowball may have started rolling and we don't know whether we can even slow it down, let alone stop it.

                          Yes, Kyoto is flawed and it is largely insufficient but it is a step in the right direction that only self-interested governments, ruled by fossil-fuel barons, have denied. It is in force, whether you like it or not. Even though the USA and Australia have not ratified the Protocol, they are both signatories and it is probable that economic sanctions will be taken against them if they do not even respect the spirit of what they have signed. What we need now is something that foresees a reduction of global GHG emissions from fossil sources by 50 - 60% by about 2025. That will be meaningful and possible by a concerted plan to exploit renewable resources, where possible with full back-up of nuclear fission using recycling of the fuel, promotion of energy conservation to the maximum (including hybrid cars with a consumption of ~4 l/100 km, in city driving, as being the only valid technology available today). However, this requires a concerted energy policy that no government has yet implemented.

                          Now, I'll surprise y'all. What is the worst fossil fuel that is commonly exploited, from the point of view of climate change? It is natural gas, even worse than coal. Of course, it is a lot cleaner than coal in that it has less impurities, but its exploitation is estimated at causing ~25% more greenhouse gas emissions into the atmosphere than coal. If you want to know more, I can point you to the calculations.
                          Brian (the devil incarnate)

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                          • #14
                            Originally posted by Brian Ellis
                            Now, I'll surprise y'all. What is the worst fossil fuel that is commonly exploited, from the point of view of climate change? It is natural gas, even worse than coal. Of course, it is a lot cleaner than coal in that it has less impurities, but its exploitation is estimated at causing ~25% more greenhouse gas emissions into the atmosphere than coal. If you want to know more, I can point you to the calculations.
                            Is this only effect of scale or perhaps even in scenario when we collect the same amount of energy from both sources the emisions from gas would be higher? (and btw Brian, have you got your Prius already?)

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                            • #15
                              Originally posted by Nowhere
                              Is this only effect of scale or perhaps even in scenario when we collect the same amount of energy from both sources the emisions from gas would be higher? (and btw Brian, have you got your Prius already?)
                              1. No the problem is because of concomitant emissions of raw methane, which is far worse than CO2. I'm preparing a web page on the subject. The first draft is at http://www.cypenv.org/world/Files/methane.htm but this is still provisional and needs a good revising, but you will get the gist.

                              2. No, the Prius is not sold here.
                              Brian (the devil incarnate)

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