Global Dimming

wiredog writes "The Guardian reports on research which shows that the amount of sunlight reaching the Earth's surface has decreased by 10% in 30 years. This has implications for global warming models and, especially, agricultural output."

Comments

Re:So instead

[WindBourne]

No. The amount of sunlight reaching earth is still the same. The amount reaching the ground is what is decreasing. It is being absorbed elsewhere or being reflected.

Re:yeah right

[Daniel Dvorkin]

sounds like complete bull to me... If ANYTHING there would be MORE now since the 70's when they implemented all the anti-smog and pollution laws. Whoever came up with these results is likely just trying to make a name for themself. Sounds like a pathetic attempt...

Did you RTFA? That's almost exactly the reaction a lot of senior scientists had, but it looks like the evidence is pretty overwhelming. (With the usual caveats about popular journalism being hard to trust when it comes to science reporting, etc.) The thing about pollution laws is, they've helped a lot, but a) a lot of pollution comes from Third World countries that have no pollution laws, or don't enforce the ones they have, and b) the effects of the laws have been pretty much overwhelmed by the fact that we have a lot more people now than we did two or three decades ago.

We've seen this on a small scale where I live, in Denver, the city that gave the world the phrase "brown cloud." When I was a kid in the Seventies, the population of the Denver metro area was about half what it is now, and the pollution was just terrible. During the Eighties, as tougher laws kicked in (AFAIK, Colorado was the second state in the western US, after California, to really get serious about this) things improved dramatically. But through the Nineties, air quality started to get worse again, and we're now just about back to where we were when the laws came into effect. Halve the average emissions, double the population ... the math ain't hard.

Re:Agricultural output

[Mr. Slippery]

Since agricultural output has already multipled and skyrocketed over the years thanks to technology and IPM, this isn't necessarily a burning crisis.

Since those yields are not sustainable, we're headed for trouble with or without global dimming.

Saying industrial agriculture is the solution to feeding our overcrowded planet is rather like saying that getting more credit cards is the solution to personal financial problems.

Driving a Truck Through This One

[occamboy]

Some datapoints:

1. In general, studies of this type are very difficult to do. One has to take into account:

• the non-continuity of the measurements (they're not measuring everywhere, they are probably tending to measure near cities; cities cause definite local effects over time, but they are only a small percentage of Earth's surface area.
• astonishingly few "scientists" actually understand how to use instrumentation. (Yeah, flame me - but it's true - I've done a lot of teaching and mentoring in this area). One of the problems of our age is that we all have access to sophisticated equipment, but few actually know what the results mean.

2. It occurs to me that if the Earth's atmosphere were soaking up all of that energy, astronemers (one group that actually does know how to use instrumentation) would have noticed spectral changes years ago. But we haven't heard from them. (They could be part of a vast right-wing conspiracy to prop up the Bush and Cheney crew, I suppose, and are just not telling us.)

3. I haven't done the calculations (has anybody?) but it also occurs to me that if Earth's atmosphere were soaking up all of that energy, there'd be some SERIOUS global warming occuring.

4. In the article, the "discoverer" of our newest Earth-dooming catastrophe seems to indicate that he was amazed to have found this issue in the mid-80's when "there was undeniable evidence that our planet was getting hotter". As some of us will recall, the dominant paradigm in the mid-80's was global cooling. Global cooling in the '80s was as obvious and well-proven as global warming is today. And, actually, diminishing sunlight reaching the Earth would be consistent with global warming (see point 3).

Re:The unintended benefits of pollution

[HeghmoH]

The thing people always seem to forget is that climate stasis is impossible even if humans had never existed. This stuff changes with or without us. We may or may not be affecting the process, but no matter what, we can't make it stay the way it is forever.

The price of uncertainty.

[e_lehman]

The important point here is: we are altering the planetary system, but can not predict the effects.

There is no doubt that we are changing the planetary system. If nothing else, CO2 concentrations are rising dramatically and human activity is definitely the culprit. And global temperatures are definitely rising. Humans may or may not be the culprit, but a back-of-the-envelope calculation suggests that more CO2 should cause higher temps.

The problem is that we can't predict the effects of these changes. It isn't like there's a global thermostat that we can turn up or down a half-degree by altering our industrial output. Rather, it is like throwing random chemicals into a bowl in a closed room, hoping you don't create toxic fumes. You might, you might not, but you don't know one way or the other, and you can't get out in any case.

I spent several months looking into climate models and concluded that they're complete bunk. We can't predict the weather a week out, but people use the very same techniques to "predict" the climate a century out. Consider this: if you believe in a human activity-climate link, then in order to predict climate, you have to predict human activity. So predicting the behavior of the entire world economy is just one small source of the uncertainty in these models! They're garbage! Computer climate models just create a false sense of predictability about climate change.

So this leaves us in a scary place. Here we are on earth. If we screw it up, we have nowhere else to go. We're making changes, but we don't know the effects. Since we don't understand the planetary system, we can't necessarily undo the effects. It's like remodeling an aircraft in flight.