The last two weeks have registered extreme heat waves in the northern hemisphere, where countries like Spain, Italy, Greece, and US (Arizona) have recorded temperatures above 40OC.

According to the World Meteorological Organisation, Europe is the fastest-warming region, with the hottest recorded summers in the last two years, where temperatures have hit 48OC.

This has affected thousands of people with increased health risks and death. Reuters News Agency has reported an estimated 61,000 heat-wave-related deaths in Europe in the last year alone.

Scientists have for a long time warned that climate change caused by greenhouse gas emissions will make heat waves more frequent, severe, and deadly.

What is climate change?

Climate change refers to the long-term shifts in temperatures and weather patterns, mainly attributed to human activities, especially the burning of fossil fuels.

Shifts in climate can be natural, but since the 1800s human activities have been the main triggers of climate change due to the burning of oil, coal, or gas that release heat-trapping gases into the atmosphere. Heat-trapping gases are what we refer to as greenhouse gases (GHGs).

Most of these gases naturally occur in the earth’s atmosphere.

How GHGS affect weather, climate 

During the day, the sun shines through the atmosphere, warming the earth’s surface. The sun generates solar radiation, part of which is reflected on hitting the surface.

At night, the earth’s surface cools, releasing heat back into the air. However, some of the heat is trapped by the GHGs that envelop the earth in the atmosphere.

This trapping is a natural phenomenon that keeps the earth’s temperature at an average of 14OC.

Without this natural GHG effect, the temperature would drop well below -18OC as the heat reflected from the earth's surface would escape to outer space.

The GHGs act “as a natural blanket around the earth” making the earth habitable. Hence, the GHGs are like a “glass ceiling”, trapping and reflecting heat to the earth’s surface.

Which are the major GHGS? 

These are carbon dioxide [CO2], methane [CH4], nitrous oxide [N2O], and water vapor.

Methane produced through decomposition has had its natural balance disrupted by human activities as large amounts are released. These include activities like cattle farming

There are also the less prevalent F-gases (fluorinated gases), which are industrial fluorinated gases like sulfur hexafluoride, perfluorocarbons, and hydrofluorocarbons.

Whereas the major gases occur naturally, F-gases are made by man during industrial processes. These F-gases appear in small concentrations in the atmosphere but are highly potent in trapping heat compared to naturally occurring gases.

Due to human activities, the carbon dioxide concentration has increased by at least 50% since Industrial Revolution began over two hundred years ago.

Methane produced through decomposition has had its natural balance disrupted by human activity as large amounts are released through cattle farming, landfills, or gas and oil production.

Large-scale use of commercial fertilisers or biomass burning is contributing to increased nitrous oxide. Water vapor, the most abundant GHG, is increasing as the earth’s atmosphere warms up.

According to Intergovernmental Penal on Climate Change, a United Nations body to advance scientific knowledge about climate change, not all GHGs have the same global warming potential as measured by the ability to trap heat.

The man-made F-gases have, though small in quantities, a much greater warming effect. For instance, sulfur hexafluoride is 23,000 times, and perfluorocarbons are 6,600 times more potent than carbon dioxide.

Furthermore, the longer the gases stay in the atmosphere, the greater the warming effect. For example, carbon dioxide stays much longer in the atmosphere compared to water vapor.

Also, the F-gases stay in the atmosphere much longer compared to other gases. Even if we stopped emitting GHGs today, it would take several hundred years before most man-made emissions are removed from the atmosphere.

The heat waves in the northern hemisphere have been attributed to the changing climate.

Sometimes, these heat waves coincide with wild fires which in turn affect livelihoods like tourism with tourists choosing cooler destinations and changing the season of travel.