Interested in a stock tip? Invest in companies that make sunscreen.

Why? Because atmospheric aerosol levels are decreasing.

An aerosol is any small particle floating in the atmosphere, like water particles, dust, and pollutants. Aerosols in the atmosphere act as a sort of global sunscreen. They scatter sunlight, reflecting some of it back into space. The less sunlight reaching Earth, the less the earth warms up.

Scientists believe that, for various reasons, global aerosol levels are going down.

This could be due to legislation in Europe and other places to curb air pollution. It's probably also partly due to natural causes. In any case, the point is that overall, more sunlight is coming through the atmosphere, and it's brighter and hotter.

Hence investing in sunscreen. You might wonder if atmospheric aerosol reflects sunlight, why not put more of it back into the atmosphere as a way to decrease global warming?

The problem is that manmade aerosols tend to pollute the atmosphere and cause asthma, allergies, and other health problems. The lesson is that if we can significantly reduce the amount of aerosols in the atmosphere, we can also reduce atmospheric greenhouse gases, which is the only real way to curb global warming.