Soot cooking the Himalayas

The Hindu Kush Himalayas make up the world’s largest region of snow and ice – known as the cryosphere. They store more freshwater ice and snow than any region outside the poles – nearly 10% of the global total. Rapid climate induced changes in the region will directly affect the water resources of more than 1.5 billion lives, as well as electricity generation, and the food supplies of three billion people. Large populations in Asia rely on the major river systems emanating from the Himalayas, with the Indus and Tarim river systems especially dependent on snow and glacier melt water.

Decrease in glacial and snow cover has been recorded across the Hindu Kush Himalayas with an increase of 1.5 degrees Celsius over pre-industrial average temperatures. Despite the complexity of observations and the lack of onsite measurements, an overall pattern of warming and melting has been apparent. The most extreme melting has occurred in the eastern Himalayas, where the mean glacial thickness of Chinese glaciers decreased by nearly 11 metres from 1985 to 2005.

A more mixed pattern is evident in the far Northwest and the Karakoram region, which are further north, colder, and more remote from large human populations and from monsoon precipitation impacts, receiving greater humidity from the west and the winter monsoon season.

This is due to global warming caused by emissions of the well-known greenhouse gas carbon dioxide, but also due to short-lived climate pollutants (SLCPs) such as soot and methane. Fast action to cut SLCP emissions will not only slow global warming, but save millions of lives, says a new study. Reductions of these will slow rapid melting in mountain regions with glaciers, like the Himalayas.

On Thin Ice, a study by The World Bank and the International Cryosphere Climate Initiative (ICCI), says that more than a million premature deaths can be avoided annually in the Himalayan region from reducing emissions of soot (also called black carbon) and methane. Such reductions will also bring multiple health, crop and ecosystem benefits, and decrease risks to development from flooding and water shortages. Measures to reduce these emissions in the Himalayan region can also increase rice and wheat yields by over 15 million tons annually.

“The health of people around the world will improve greatly if we reduce emissions of black carbon and methane. Limiting these emissions also will be an important contributor to the fight against climate change,” Jim Yong Kim, World Bank president, said at the release of the report.

The report warns that current warming in the cryosphere can have dire human consequences from resulting sea level rise, increased water stress and more extreme weather. For example, the release of large carbon dioxide and methane stores as a result of melting permafrost can contribute up to 30% more carbon to the atmosphere by the end of the century.

Many glacial lakes have formed or expanded during the rapid melt process in eastern and central Himalayas. These have led to so-called glacial lake outburst floods (GLOFs) — especially in Nepal and the Tibetan region. Other GLOFs have been narrowly averted there and in Bhutan by implementing measures such as siphoning off melt water, as occurred with Tsho Rolpa in Nepal.

The importance of melt water from greater Himalayan glaciers and snowpack to human water supplies varies widely. Estimates range from 80% dependency of overall river flow on melt water in the western regions, especially the Indus and Tarim river basins, to under 20% in the Yangtze, Ganga and Yellow rivers. A 2013 report by the Asian Development Bank categorised Pakistan as one of the most water-stressed nations in the world, largely due to changes already seen in the supply to the Indus river.

Global warming means more uncertainty for the south Asian monsoon, around which local populations have based their agricultural practices for millennia. The past decade has seen a general decrease in overall rainfall during the monsoon and a later date of onset. At the same time, the region has seen an increase in extreme events, such as the flooding in Uttarakhand in northern India in June 2013 that killed nearly 6,000 people, and in which rainfall-induced heavy melting of the Chorabari Glacier was also implicated.

The report points out that a direct relationship between Himalayan conditions and the monsoon is highly uncertain. But at the same time, studies of air pollution-related climate impacts and the Atmospheric Brown Cloud (ABC) seem to indicate a large impact from regional sulphate and particle emissions on monsoon precipitation levels and timing.

Greater uncertainty in water supply for local agriculture — in many cases, marginal to begin with — is itself an impact to be avoided. As in the Arctic, permafrost melt is also of concern in the greater Himalayas, especially on the Tibetan Plateau, where much of the infrastructure such as highways, rail lines and dams has been built over frozen ground. The permafrost of this region is unique and ancient, formed over the past two million years through uplift of the Himalayas and the Tibetan Plateau. Due to the arid nature of this region, the permafrost is relatively fragile, and its extent has decreased by nearly 20% over the past 30 years, with an increase in average permafrost temperature documented since 1996.

“The cryosphere is changing fast as a result of climate change, it is changing today, and those changes bring increased risk to ecosystems and human societies,” said Pam Pearson, ICCI director. “If warming continues unabated, the risks from continuing sea level rise, flooding and water resource disruption rise dramatically. This report makes clear that slowing cryosphere warming is an issue of global concern. Also, that action to cut SLCPs must take place in concert with ambitious efforts to cut long-lived greenhouse gases.”

The report lays out 14 specific measures the world can take by 2030 to reduce SLCPs and slow the melting of ice and snow that must stay frozen to keep oceans and global temperatures from rising even faster.

Recommended Reduction Measures

If four cleaner cooking solutions are quickly scaled up, a million lives can be saved every year. That is a quarter of the mostly women and children who die from exposure from indoor and outdoor cooking smoke annually – higher than the annual toll of HIV/AIDS, malaria, and tuberculosis combined. All the while, the warming impact of black carbon from these cook-stoves on polar and mountain regions would be reduced, especially in the Himalayas.

A 50% drop in open field and forest burning – another leading source of black carbon – can result in 190,000 fewer deaths from air pollution. Reducing emissions from diesel transport can avert yet another 340,000 premature deaths, while providing some quick gains in the combat against climate change.

Reductions in emissions from diesel transport and equipment can result in more than 16 million tons of additional yield in crops such as rice, soybean and wheat, especially in Southeast Asia, and also avert 340,000 premature deaths. Emissions of methane, as well as nitrogen oxide from diesel use, cause higher levels of ozone which result in lower growth of food crops, and thus a decrease in crop yields.

The report however makes it clear that reducing SLCPs is no substitute for reducing carbon dioxide emissions. But it can be complementary. “Though global decreases in CO2 (carbon dioxide) cannot and should not be replaced, many communities have it in their power to at least slow snow and glacier loss nearby” by reducing soot and methane emissions, say the authors.

Climate benefits for cryosphere regions from black carbon emission reductions carry less uncertainty than they would in other parts of the globe and are sometimes very large. This is because emissions from sources that emit black carbon — even with other pollutants — almost always lead to warming over reflective ice and snow.

Talking about the need to reduce emissions of methane – another potent GHG – the report points out, “While CO₂ emissions primarily come from fossil fuel use, significant methane and black carbon emissions arise in the production chain for oil, gas, and coal (approximately 65% of benefits from all methane measures), strengthening the need for conversion to low-carbon economies.”

It says black carbon and methane emission reduction measures can mean the Himalayan cryosphere may see nearly a one-degree Celsius decrease from baseline projections, though there is significant uncertainty around this prediction.

The authors warn, “The window for action is closing fast.” The benefits outlined in the report are based on the assumption that necessary steps will be taken by 2030.

See: Study soot to understand melting rate of glaciers
See: Fire and ice: soot darkens Himalayan glaciers