Tropical rains will shift northward in coming decades

The world is no stranger to the effects of climate change, but the coming northward shift of tropical rain due to unchecked carbon emissions could have profound impacts on agriculture and economies around the equator.

This potentially drastic change could significantly affect equatorial regions. Countries around the Equator on both sides, such as Central African countries, Northern South America and Pacific Island countries, are expected to feel the effects most acutely.

Tropical Rainfall Change and Atmospheric Changes

A northward shift in rainfall has been predicted by a team of researchers at UC RiversideLed by Atmospheric Scientist Professor Wei Liu.

Precipitation change is primarily associated with complex atmospheric changes caused by carbon emissions, which in particular affect the formation of tropical convergence zones.

Described as atmospheric engines, tropical convergence zones are responsible for generating one-third of the world’s rainfall.

Impact on major tropical crops

Many important tropical crops are grown in areas expected to be most affected by changes in rainfall.

Coffee, cocoa, palm oil, bananas, sugarcane, tea, mangoes and pineapples are among the agricultural commodities that may see production problems due to the instability of rainfall.

However, this northward shift only lasts about 20 years. Following this period, due to the warming of the Southern Oceans, the convergence zones are expected to move back south, remaining in this position for nearly a millennium.

Understanding the Tropic Convergence Zones

Tropical Convergence Zones essentially act like a conveyor belt for moisture. Located at or near the equator, these zones are where the trade winds from the northern and southern hemispheres meet.

Colliding air currents rise upward to cooler altitudes, and as they do so, they absorb large amounts of moisture from the oceans.

As this moist air cools at higher altitudes, thunderclouds form, and drenching rainstorms are unleashed. It is not unusual for tropical rainforests to receive 14 feet of rain per year.

Atmospheric impact of carbon emissions

Scientists used advanced computer models to simulate the real-world effects of continued fossil fuel burning and other carbon dioxide emissions. The complex model includes various components of the atmosphere, ocean, sea ice, and land, with each component interacting with the others.

Professor Liu and his colleagues use these sophisticated computer models to predict the atmospheric influence of carbon dioxide emissions.

„Rain change is very important,” Liu said. “It is a very high rainfall area. Therefore, a small change can lead to big changes in agriculture and the economy of communities. It will affect many regions.

„Basically, we’re trying to simulate the real world. In the model, we can increase our carbon dioxide emissions from pre-industrial levels to very high levels.

Researchers also factor in how carbon emissions affect the amount of radiative energy at the top of the atmosphere, sea ice changes, water vapor variations and changes in cloud formation.

The combined effects of all these factors push the rain-producing convergence zones northward by an average of 0.2 degrees.

Influence of tropical rain patterns

In conclusion, although the effects of climate change are many and varied, a potential short-term shift in tropical rainfall patterns could have long-term effects on the agriculture and economies of communities near the equator.

This significant change underscores the urgency to effectively address global carbon emissions.

The study is published in the journal Natural climate change.

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