Pollution slows warming?

[Dr Mordrid]

PopSci Link....

According to the study, temperatures in Europe have risen over the past 28 years far faster than could be explained by the greenhouse effect alone. After looking at the aerosol concentrations in the atmosphere in six spots, the authors of the paper realized the temperature rise was assisted by more sunlight penetrating the newly pollution free skies. It seems that the stricter pollution standards, adopted in part to slow global warming, may have sped it up.

The idea that pollution may be reflecting some of the sun’s energy is not new. The term global dimming is decades old, and some believed that the reduction in pollution was the cause global warming. But now, with the link between greenhouse gas pollution and global warming firmly established, papers like this one highlight how complex the situation is, and how solutions like simply cutting air pollution may have a range of unintended and counterintuitive consequences.

American Geophysical Union abstract:

The rapid temperature increase of 1°C over mainland Europe since 1980 is considerably larger than the temperature rise expected from anthropogenic greenhouse gas increases. Here we present aerosol optical depth measurements from six specific locations and surface irradiance measurements from a large number of radiation sites in Northern Germany and Switzerland. The measurements show a decline in aerosol concentration of up to 60%, which have led to a statistically significant increase of solar irradiance under cloud-free skies since the 1980s. The measurements confirm solar brightening and show that the direct aerosol effect had an approximately five times larger impact on climate forcing than the indirect aerosol and other cloud effects. The overall aerosol and cloud induced surface climate forcing is ∼+1 W m−2 dec−1 and has most probably strongly contributed to the recent rapid warming in Europe.


Received 9 April 2008; accepted 22 May 2008; published 24 June 2008.

[Marshmallowman]

As I understand sulphur is an "anti-green house gas" in that it tends to reflect more heat from the atomsphere, having said that acid rain from SO2 is not a good thing

[Dr Mordrid]

I think they are talking aerosols in general, not just SO2.

[Marshmallowman]

fair enough, I was just throwing up an cas/example why i think it is a real a possibilty

[Brian Ellis]

There are several phenomena relative to this here. Firstly, aerosols tend to see cloud formation with a higher albedo so that a reduction of clouds may increase radiation forcing. Aerosols can also directly reduce irradiance at the earth's surface. However, there are aerosols and aerosols. Stratospheric aerosols are increasing, mainly because of increased aircraft traffic. Some tropospheric aerosols, largely related to industrial and domestic coal burning, has decreased very significantly, whereas those due to the massively increased use of diesel engines has increased. The particle size and nature of these are very different. Then there are those formed by photochemical reactions with hydrocarbons, which have also increased.

It is incorrect to equate SO2 with aerosols. SO2 is a gas that readily oxidises to another gas, SO3. Both rain out at low tropospheric levels and do not form aerosols. OTOH, the -SO4-- or sulfate anion is found in molecules forming mainly stratospheric aerosols and is produced from volcanic eruptions and the flight of aircraft not using desulfurised fuel (such as Jet Avaiation A).

However, there are other factors that must be considered. The famous "Azore anticyclones", producing periods of several days of cloudless skies, have moved northwards and cover more of Europe than in yesteryear. In my opinion, weather and climate are so full of complex inter-relations with both negative and positive feedbacks that one cannot isolate one parameter, such as aerosols, and state categorically that these alone have done this or that, without much more complex calculations. Notwithstanding, they may be contributory, the same as retreating ice may be contributory. Notice: "most probably strongly contributed" They do not state "causal".