According to the recent studies, the pollution caused by people makes the tropics and sub-tropics shift towards the poles. This study also says that the pollutants include black carbon soot and tropospheric ozone.
The spreading out of the tropics happens at the rate of 0.7° latitude in one century. Naturally the greenhouse gases also contribute to the warming, thus supporting the expansion in both of the hemispheres.
Changes that matter
As a result of this change, as the tropics are pushed poleward, the sub-tropics are becoming drier and drier. If such a displacement takes place in the mid-latitude as well, the results could include an impact on the local economy, agriculture and society.
In order to perform the studies, the specialists compared the data from 1979 to 1999. In the base-case scenario when the specialists didn’t take into consideration the pollutants that were mentioned before, the results showed a shift of 0.35°.
However when one of these pollutants was added as an acting factor, the results got closer to reality. This suggests that these pollutants have a key role in tropical expansion.
After this the specialists extended their research period to 1999-2009 as well. The specialists repeated the same studies and they managed to isolate the effects of the pollutants on the tropics. Just as in the first case, in the base-case scenario the effects were underestimated. When the specialists also took into consideration the pollutants, the simulations got closer to the actual observations.
What exactly happens?
Both of the pollutants that the specialists were working with make the tropical regions warmer by absorbing the radiations of the sun. We also have to add that these pollutants have short life spans, of only 1-2 weeks. This is why the concentration is the highest around the source. Since a lot of these pollutants come from the northern hemisphere, the tropical regions are pushed downward.
We also have to take into consideration that the wind patterns follow the same trend. These influence some other aspects of the atmospheric circulation as well, precipitation for instance.
Black carbon aerosols are small carbon particles that come from burning of biomass and from the incomplete burning of fossil fuels. The majority of the pollutant production comes from the northern hemisphere, one of the major contributing regions being Southeast Asia.
All these explain the weather and climate changes that we can see all over the world and they should become a sign of alarm.