By Avigayil Kadesh
No matter what else is going on in the world, there is no hotter topic than the weather, and even more so in the past few years when weather-related natural disasters seem to be on the rise. Is it because of manmade pollution from traffic and industry? That is a subject of intense debate.
Recently, a leading Israeli professor of atmospheric sciences unveiled the first-ever method to provide standardized global testing of pollution levels.
Prof. Pinhas Alpert of Tel Aviv University's Department of Geophysics and Planetary Sciences, and head of the Porter School of Environmental Studies, tapped into three NASA satellites for eight years' worth of comprehensive data.
Working with graduate student Olga Shvainshtein and scientist Pavel Kishcha, Alpert tracked pollution trends for 189 cities with a population exceeding two million -- 58 of them, including New York City, Tokyo, and Mumbai, with populations of more than five million.
Their accumulated data show that northeast China, India, the Middle East and Central Africa are currently leading in pollution increase. Bangalore, India, and Ibdan, Nigeria, had the greatest average increase in aerosol concentration between 2002 and 2010.
On the positive side, Europe and northeast and central North America are seeing the largest decreases in aerosol concentrations overall. Among the cleanest cities were Houston, with a 31 percent decrease over the time period; Curitiba, Brazil, with a 26% decrease; and Stockholm, Sweden, with a 23% decrease.
A more accurate picture
A global standardized approach to smog analysis has been elusive until now, Alpert explains. The problem is not only that data coming from on-ground monitoring stations is unreliable, but also that many governments do not like to publicize accurate numbers on pollution. In addition, some parts of the world have no monitoring stations at all.
So Alpert and his team decided to gather data from three aerosol-monitoring satellites -- MODIS-Terra, MODIS-Aqua, and MISR -- that NASA launched from 2000 through 2002 to measure aerosol concentrations a few hundred meters above Earth.
Why didn’t anyone think of this before?
Alpert explains that the NASA personnel involved in collecting data from each satellite are hesitant to use it broadly because they are aware of the flaws in their own system.
“I did my sabbatical at NASA years ago, and I know this group well,” says Alpert. “I realized because of the complications in each satellite they were reluctant to go ahead. Indeed, each instrument has its own problems that are not necessarily the same as the others.
“But when you collect from the three instruments together, in spite of their different algorithms and instrumentation and angles from space, their flaws are mostly counterbalanced and they do agree concerning most of the cities in the world. Sometimes there is agreement between two of the three, and in such cases we suggested looking at the majority.”
He even gave his methodology a Jewish spin when he presented his findings to 100 algorithm developers last July at NASA. "In the Jewish tradition, individual judges don't decide cases. There must be a minimum of three. You need a majority opinion," he explained.
Alpert says his audience listened intently and continued the discussion afterward.
“They were amazed that somebody from the ‘outside’ came and did this,” says Alpert, who in 2009 won a Popular Science award for his flood-warning invention.
The next step
Alpert is continuing to fine-tune the satellite for use in planning and policy to combat the health and environmental problems caused by the thick atmospheric layer of pollutant particles.
“We already did joint work with NASA scientists, not yet ready for publication, where we investigated more thoroughly what happened in the northwest United States,” he says.
Portland, Oregon, and Seattle, Washington, had each shown alarming increases in pollution, but Alpert suspected this was due to the multiple wildfires in the region during the second half of the period examined. Their further research proved him correct. Now he must figure out how to quantify separately the pollution caused by the fire and pollution caused by human factors such as hazardous litter, including plastic, which burned in the fire.
His ultimate goal is to offer bodies such as the United Nations an objective and consistent basis for working toward mitigation of climate change without relying on ground reports.
“Using the same algorithm to calculate for the whole world, we can really get more objective methodology for monitoring pollution,” he says, “but first we must address problems such as fires.”
International treaties aimed at reducing pollution could use this measuring stick to keep countries accountable for their promises by tracking compliance in an equitable way. Cities that successfully decrease pollution could be applauded for their efforts and stand as a positive example to follow, suggests Alpert.