Global Dimming vs Global Warming

I think that we may have overlooked something.  It is a phenomenon called Global Dimming, which is caused by pollution both natural from bushfires and manmade from industrial particulate emissions.  It has been shown that Global dimming provides a dampening effect for Climate Change. 

Now, it is a bit difficult to explain the effect but suffice to say that the pollution particulates block some of the energy of the sun from reaching the ground, therefore less heat.  Apparently during the 3 days after the 9/11 attack when all commercial aircraft were grounded, on scientist discovered that just by removing the pollution from the contrails of the aircraft (which is only one small portion of global pollution on a daily basis), the average temperatures throughout the US rose on average by 1°C for the period.  It doesn’t sound like much, but neither does the 0.6°C rise in average global temps we have experienced so far, and that small change is causing the northern ice cap to reduce every year, and melt glaciers all over the world!

So as we reduce particulate pollution, like via catalytic converters on cars, and enforce stronger pollution controls from diesel fuels, we must at the same time reduce the green house gas emissions or we face a rapid escalation in global warming.

I don’t think I have articulated it very well, so I found this series of videos on YouTube that make up one documentary made by the BBC titled ‘Global Dimming’ which explains all the science, how the effect was discovered and what would happen if we tackle one issue without tackling the other at the same time.  I hope you take the time to watch it.  It certainly opened my eyes to another issue that I wasn’t aware off and that will effect us all soon enough.

Global Dimming Documentary Part 1/5

bbc Climate change- global dimming part 2

Climate Change — Global Dimming part 3

Global Dimming Documentary Part 4/5

Global Dimming Documentary Part 5/5

Interesting and alarming at the same time!



  1. says

    Thanks for the great article. It helped me to completely understand what global dimming is all about. I will be sharing this article with my friends. Again, thanks for sharing.

  2. Luke says

    This certainly sounds plausible (and concerning) and should encourage us all to work harder to achieve strong emissions cuts.

    Now I haven’t watched the videos, but I am a bit concerned with the figures you quoted re the aftermath of September 11 in the post Gavin. I have heard that astronomers the world over were pleasantly surprised with the reduction in high altitude pollution (from jetliner contrails), but the temperature rise you quote (probably straight from the documentary) seems implausible.

    Firstly a three day measurement period is nowhere near long enough to be statistically significant, after all, look at the nightly news, the weathermen are always telling us that such and such a day is x degrees warmer/cooler than average, and the chances of getting 3 days 1 degree warmer than average would probably be reasonably high and therefore difficult to attribute to the reduction in pollution.

    Secondly, if the removal of a relatively small portion of global pollution can cause such a significant rise in temperatures, what does that imply for the reduction of all pollution? I’m not sure what model the relationship follows (linear, quadratic, exponential or something else) but then what would the hypothetical removal of all airborne pollution result in? A 5 degree rise? 10 degrees? Obviously we’d all be pretty stuffed if that were true, but it seems implausible that such a small reduction in pollution could cause such a large impact.

    Don’t get me wrong, I think the basic premise of the documentary is sound, since we have precedents of increased pollution leading to cooling after volcanic eruptions, but I just can’t stomach those particular figures.

  3. says

    @ Belinda. So true, I think that may already be on the drawing board of one of the geo-engineering solutions to climate change.

    @ Micah. Thanks for the praise. I will check out your blogs tonight

    @ Anon from Chicago, Illinois. Either put up or shut up. The science is in for both issues.
    Get your head out of your arse and take a look at the evidence around you. We are the cause of this particular instance of climate change in global history!
    Also, I hate sceptics who hide behind the anonymous tag. Have the courage to use your name next time and I might have a civilised debate.


  4. Anonymous says

    Are you people for real? Do you NOT remember that this reasoning was used during the cooling period from the 40’s to the 70’s? Can’t you just accept that the earth goes through normal periods of warming and cooling? In other words, “MAN” has VERY little to do with controling climate change.

  5. says

    This is a great post.. Very informative… I can see that you put a lot of hard work on your every post that’s why I think I’d come here more often. Keep it up! By the way, you can also drop by my blogs. They’re about Vegetable Gardening and Composting. I’m sure you’d find my blogs helpful too.

  6. says

    I agree, interesting and alarming. One of the things that I find particularly alarming is the idea that some bright spark may decide the best way to bring global temperatures down without people having to lift a finger is to throw other types of particulate matter into the atmosphere.

    Sure it may reduce global temperatures but it has real potential to ensure that food production is severely affected.

    Until us human beings get a handle on the fact that everything we do has consequences within areas we are not trying to change it’s all only going to get messier.

    Kind Regards

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