In “Climate change 101”, a brand-new weekly column by Carolien Samson, head of sustainable banking at Oxbury Bank Limited, we zoom into all things climate change – what it is, responses to it and how it could affect farmers in Africa and beyond.
Climate change – it is a field that has developed a technical jargon of its own, complete with acronyms by the dozen, but we all need to understand this much better as agriculture is one of the few sectors that both contribute to and reduce the impact thereof.
Ever heard Earth described as a planet in the “Goldilocks” zone – not too warm, not too cold to allow organisms to survive? The process to maintain that temperature level is called the greenhouse effect.
The sun heats the earth when some of the solar energy is absorbed by the earth’s surface – the oceans, forests and land. Some of the solar energy is reflected back into the atmosphere by areas such as snow-covered polar caps. Once the energy is absorbed by the earth, it is converted and infrared (heat) energy is emitted by the earth’s surface.
Some of that infrared energy passes through the atmosphere, but some of the infrared energy is absorbed by greenhouse gases and re-radiated in all directions back to the earth. The greenhouse gas was first described by French physicist Joseph Fourier in 1824.
What are the main greenhouse gases?
A greenhouse gas is defined as any gas that absorbs infrared energy. There are several types of these gases, but the main ones are carbon dioxide (CO2), water vapour (H2O), methane (CH4), and nitrous oxide (N2O).
Despite making up a fraction of all the atmospheric gasses, the greenhouse gases have a significant impact on earth’s climate. These gases are created through natural processes like volcanic outbursts as well as human activity like agriculture, vehicles using oil-derived petrol and coal-fired electricity.
For millions of years, natural processes were the main drivers of the release into and removal of these gases from the atmosphere, but since the start of the Industrial Revolution in the 18th century, human activity have released greenhouse gases at such a pace that it now affects the temperature regulation of the planet.
The gas particles have different average lifespans in the atmosphere with methane being around for a decade, carbon dioxide about a millennium and nitrous oxide about a century.
The rate at which carbon dioxide particles are increasing in the atmosphere have been measured consistently since 1958 when Dave Keeling started an experiment at Mauna Loa in Hawaii. Since that time, carbon dioxide concentration has increased from 320 particles per million to more than 420 by May 2022. Older information is obtained by analysing ice samples from glaciers and the poles and other natural sources.
So what is global warming?
Global warming refers to the long-term increase of the earth’s average temperature due to the greenhouse effect. Increased levels of greenhouse gas particles in the atmosphere absorbs more and more heat, thus preventing the heat from escaping back into space.
Way back in 1886, Swedish chemist Svante Arrhenius, first pointed out that the coal-burning processes of the industrial era will impact the greenhouse effect and his calculations remain remarkably accurate.
And climate change?
Although the terms global warming and climate change are often used interchangeably, they are not the same. Climate change is the result of global warming and refers to the changes in weather patterns, sea levels and ice sheets as a result of the temperature increase.
Climate models constructed by various scientific bodies across the world are used to assess the potential outcomes for different regions in the world. These are models are also informed by the geological record of the planet as there have been periods of similar temperature over millennia.
What the world could look like
The greenhouse effect is a completely natural process and has happened since the earth formed a planet. The planet has cycled through periods of warmer weather following long ice ages for millions of years.
As recently as 50 million years ago the earth had much higher carbon dioxide levels and early mammals were struggling to survive in a tropical atmosphere that engulfed the planet. Much of the carbon dioxide was absorbed when the Indian subcontinent finally met up with Asia and created the Himalayas which became a large carbon sink.
Once carbon levels reduced, millions of years of Ice Ages followed, broken by periods of milder temperatures. About 3 million years ago, we find a period where carbon dioxide levels were similar to current levels.
But we won’t recognise the world where the Namibian and Sahara deserts were covered in savannah, woodland and lakes and giant animals still roamed.
The outline of the continents would be different as miles of today’s coastal areas are under a sea nearly 30 meters higher than current levels. Not far from the South Pole trees exist, remnants of a forest from an even warmer age.
There are more recent examples going back 120 000 to 20 000 years ago which are also instructive in what could occur.
Let’s talk weather…
The weather is the local condition of the atmosphere at a specific time like an hour, day or month. Climate change may affect local weather patterns making areas on average hotter or colder, wetter or drier, more or less prone to storms than recent historical patterns.
Climate describes the typical weather conditions at that time or year or season for a specific region based on long-term trends and averages. The Western Cape is in a winter rainfall area describes the climate, while the fact that there was snow in Ceres in August is a weather event.
For farmers it is therefore important to understand how local weather will be impacted by climate change as that affects their planning and decisions.
In the next article we’ll consider how farming both contributes to the greenhouse effect and mitigate the impact.
ALSO READ: Climate change: Women in farming need support
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