But besides causing 700 extra deaths a day in Moscow alone - due to the smoke from forest fires, according to its top health official - the smoke is hastening the melting of Arctic ice.
Forest and peat bog fires around Moscow are burning over 1,740 sq kms (672 sq mile), the Russian Emergencies Ministry says.
Similar fires in Asia are having a similar effect on glaciers in the Himalayas.
On the other side of the planet, official Brazilian data shows the Amazon rainforest lost 1,810 sq kms in almost a year to June 2010. The real figure is likely to be higher.
Brown clouds also form over parts of North America, Europe, the Amazon basin and southern Africa. Burning of savannah in sub-Saharan Africa, to clear land for crops, is a new source.
"Health effects of such clouds are huge," said Veerabhadran Ramanathan, chair of a new U.N. Environment Programme (UNEP) study called Atmospheric Brown Clouds.
This report says there are five hot spots for such clouds:
- East Asia
- Indo-Gangetic Plain in South Asia
- Southeast Asia
- Southern Africa; and
- the Amazon Basin.
But the effects can be felt far away...
Melting Greenland
A team from Aberystwyth University currently doing research in Greenland has found unprecedented levels of melting of the Greenland ice sheet.
A key factor, they have discovered, is cryoconite, a form of ice dusted with minute specks - a mixture of desert sand blown thousands of kilometres from Africa, soot particles from power stations, vehicle exhausts and microscopic algae and bacteria.
These particles settle on the ice and, being dark, absorb the sun's rays, causing it to melt.
Besides that, the UNEP report says this atmospheric smog is near-permanent and blames it for causing chronic respiratory and heart diseases.
Since 1970, southern Greenland has warmed by 3oC (in Britain it is half of a degree). A week ago, a massive iceberg 100sq miles in area broke off the Petermann Glacier in the north-west of the island and floated into the ocean - the largest chunk of ice to break off Greenland for nearly half a century.
Greenland is losing, net, about 267 billion tons of ice a year, according to Aberystwyth University's Dr Alun Hubbard, Britain's leading glaciologist studying Greenland.
He says that two weeks ago an ice lake 2.5 miles across drained into the sea in just two hours when a crack opened up at the lake's deepest point.
He said it sounded like "an extraordinary rumbling, like an atomic bomb going off ". Ominous cracks opened up in the ice beneath his camp's tents as the lake was swallowed by the ice.
Such melt-water flows underneath the ice sheet to the sea, at the same time lubricating the passage of the ice above it and accelerating it towards oblivion. Exactly the same process is happening in the Himalayas and Antarctica.
If all of Greenland's ice were to melt, sea levels would rise by seven metres worldwide. London and Liverpool would be flooded. Hwever, current estimates are that this is unlikely to happen until a few hundred years have passed.
A reporter with the Daily Mail, embedded with the Aberystwyth University team, wrote this week that "Sceptics will argue that Greenland has always had moulins and meltwater rivers; this is true. But what is new is these used to be confined to the very edge of the icesheet, marginal, ephemeral features that lasted just a few weeks in the height of the summer melting season. Now there are lakes and moulins right on the centre of the cap, and persisting well into August."
When the normally sceptic Daily Mail and its climate change-denying columnist Michael Hanlon runs pieces like this, you know something is going on.
Brown clouds
"The Russian fires are in principle similar to what you see from other brown clouds," said Henning Rodhe of Stockholm University, a vice-chair of the UNEP Atmospheric Brown Cloud (ABC) study. "The difference is that this only lasts a few weeks."
Elsewhere, however, the polluting haze blocks out sunlight and so slows climate change. Despite this, overall, the report says, the brown clouds have the net effect of "heating of the surface-atmosphere system and therefore constitute a positive radiative forcing of the climate system and contribute to global warming. Thus, black carbon aerosols are major agents of regional and global warming."
The report says that in the Himalayas, "If the current rate of retreat continues unabated, these glaciers and snow packs are expected to shrink by as much as 75 per cent before the year 2050, posing grave danger to the region’s water security. Projections show that most parts of South and East Asia will suffer from water stress by 2050."
Mega-city hotspots
13 mega-city ABC hotspots in Asia have been identified: Bangkok, Beijing, Cairo, Dhaka, Karachi, Kolkata, Lagos, Mumbai, New Delhi, Seoul, Shanghai, Shenzhen and Tehran.
Kim Holmen, director of research at the Norwegian Polar Institute, runs a pollution monitoring station in Svalbard in the high Arctic. He says the air over Russia has been fairly stable in recent days, but a shift in winds could blow the smoke towards the Arctic.
He supports Russian authorities' concerns that the fires may also release radioactive elements locked in vegetation since the Chernobyl nuclear disaster of 1986. He says radioactive isotopes include strontium 90 and caesium 137. Other industrial pollutants such as PCBs could also be freed.
"Such conditions are likely to become more common in the future," Rodhe said of the Russian heatwave and related fires.
If they are, sea level rise is likely to accelerate at a faster rate than would be anticipated if only linked to a global average temperature rise.
Arctic sea ice, which shrinks in mid-September to an annual minimum before the winter freeze, now covers a slightly bigger area than in 2007 and 2008, the smallest extents since satellite measurements began in the 1970s.
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