Global Warming May Increase with Rising Water Vapor in the Atmosphere

What might cause global warming to increase in the next few decades? It could be water vapor. Scientists have found that rising levels of water vapor in the upper troposphere will intensify climate change impacts over the coming years.

Greenhouse gases raise the temperatures on our planet by trapping Earth's radiant heat inside the atmosphere. This warming also increases the accumulation of atmospheric water vapor, which is the most abundant greenhouse gas. The atmospheric moistening traps additional radiant heat which then increases temperatures.

For the past 30 years, there's been a moistening trend in the upper troposphere, which is a region about 3 to 7 miles above Earth's surface. That's why scientists wanted to see exactly what effect this moistening might be having on the climate, and the impacts it might have in the future.

The researchers measured water vapor in the upper troposphere collected by NOAA satellites. Then, they compared this data to climate model predictions of water circulation between the ocean and the troposphere in order to see whether the changes in water vapor could be explained by natural or human-induced causes.

So what did they find? It turns out that the rising water vapor can't be explained by natural forces. Instead, it's probably due to increased greenhouse gases.

"The study is the first to confirm that human activities have increased water vapor in the upper troposphere," said Brian Soden, co-author of the new study, in a news release.

The findings reveal that as people burn fossil fuels, the concentrations of water vapor will also increase in response to warming. This, in turn, will absorb even more heat and contribute to the rising temperatures. The new research could have implications for climate models and also show how multiple factors play into our warming planet.

The findings are published in the journal Proceedings of the National Academy of Sciences.