As it cools during the boreal winter months, the rains return south.
During the boreal summer months, the tropical and mid-latitude rain belts migrate north as the northern hemisphere warms. Over the past 50 years, the middle and high latitudes in the northern hemisphere have warmed roughly twice as much as the corresponding latitudes in the southern hemisphere, and this disparity may continue to grow as Arctic sea ice continues to decline.Ī smaller, seasonal north-south migration of the thermal equator occurs today. This shift caused widespread changes in global precipitation, write the authors.Ī similar situation may be setting up. The temperature contrast between the two hemispheres caused the thermal equator and the associated tropical rain belt and the mid-latitude jet streams to shift northward. As a result, the northern hemisphere warmed more quickly than its southern counterpart. Putnam, a professor of Earth and climate sciences, and co-author Wally Broecker, Newberry Professor of Geology at the Lamont-Doherty Earth Observatory at Columbia University, find support for their predictions in the paleoclimate records that chronicle the abrupt warming of Earth’s climate during the transition out of the last ice age nearly 15,000 years ago.Īs the Earth abruptly warmed at the end of the last ice age, sea ice in the northern hemisphere rapidly declined as Antarctic sea ice expanded. However in the boreal winter, the Earth’s thermal equator, which governs the location of the planet’s rain belts and dry zones, will migrate northward as a response to differential heating between the hemispheres.Īs a result, areas in the tropics will become much wetter and the drylands of the western United States, inner Asia and the Middle East will become even drier. The researchers, led by University of Maine glacial geologist Aaron Putnam, predict a seasonal response in rainfall patterns as a result of overall global warming.ĭuring the boreal, or northern hemisphere’s, summer, wet areas will get wetter and dry areas will get drier. "Although we have found that this process is happening slower than first thought, if global warming exceeds 3☌, wet regions will likely get more than 10 per cent wetter and dry regions more than 10 per cent drier, which could have disastrous implications for river flows and agriculture."ĭr Skliris added "The agreement between climate models and observations over the recent past is another important finding of this study because it adds confidence to climate model projections of water cycle amplification under greenhouse gas emission scenarios.Climate Change, Research, Signature and Emerging AreasĪs the world warms due to human-induced climate change, variations in the global distribution of rainfall can be expected, impacting water resources in many places on Earth, according to a new study published in the journal Science Advances. The research team believe this is probably due to a weakening of the atmospheric circulation which transports freshwater from the dry to wet regions of the globe.ĭr Nikolaos Skliris, a Research Fellow at the University of Southampton who led the study, said: "Our findings match what has been predicted by models of a warming climate as the world gets warmer wet regions will continue to get wetter and dry regions will continue to get drier. The new study estimates that amplification happens at about three to four per cent per 1☌. Previous research indicates that amplification of the water cycle, is happening at 7 per cent per 1☌ of global warming. This process is called amplification of the water cycle. The researchers found that the regions, which are relatively wet, like Northern Europe are getting wetter and dry regions are getting drier both by about 2 per cent over the last 60 years. The researchers used measurements of salinity throughout the global and deep oceans over the last 60 years to estimate how much global rainfall is changing. More evaporation in another region takes away fresh water and leaves salt behind making that region more saline. More rain and outflow from rivers in a region of an ocean means sea water gets diluted and therefore becomes less salty.
The study, published in Scientific Reports, analysed the saltiness of the world's oceans.