In “Climate change 101”, a brand new weekly column from Caroline SamsonHead of Sustainable Banking at Oxbury Bank Limited, we look at all things climate change – what it is, responses to it and how it could affect farmers in Africa and beyond.
Climate change – it is an area that has developed its own technical jargon, with dozens of acronyms, but we all need to understand it better because agriculture is one of the few sectors that both contributes to it and reduces its ‘impact.
Have you ever heard that Earth was described as a planet in the “Goldilocks” zone – neither too hot nor too cold for organisms to survive? The process of maintaining this 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 returned to the atmosphere by areas such as the snow-covered polar caps. Once the energy is absorbed by the earth, it is converted and infrared energy (heat) is emitted from the surface of the earth.
Some of this infrared energy passes through the atmosphere, but some of the infrared energy is absorbed by greenhouse gases and reflected in all directions back to 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 vapor (H2O), methane (CH4), and nitrous oxide (N2O).
Although they constitute only a fraction of all atmospheric gases, greenhouse gases have a significant impact on the Earth’s climate. These gases are created by natural processes like volcanic eruptions as well as human activity like agriculture, vehicles using petroleum-derived gasoline, and coal-fired electricity.
For millions of years, natural processes have been the primary drivers of the release and removal of these gases from the atmosphere, but since the start of the Industrial Revolution in the 18th century, human activity has released greenhouse gases at such a rate that it is affecting the planet’s temperature regulation.
Gas particles have different average lifetimes in the atmosphere, with methane being present for a decade, carbon dioxide around a millennium, and nitrous oxide around a century.
The rate at which carbon dioxide particles increase in the atmosphere has been measured consistently since 1958, when Dave Keeling began an experiment at Mauna Loa in Hawaii. Since then, the concentration of carbon dioxide has increased from 320 particles per million to over 420 in May 2022. Older information is obtained by analyzing ice samples from glaciers and poles and other natural sources.
So what is global warming?
Global warming refers to the long-term increase in the Earth’s average temperature due to the greenhouse effect. Rising levels of greenhouse gas particles in the atmosphere absorb more and more heat, thus preventing heat from escaping into space.
In 1886, Swedish chemist Svante Arrhenius first pointed out that industrial age coal combustion processes 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 changes in weather patterns, sea levels and ice caps as a result of increased temperature.
Climate models built by various scientific organizations around the world are used to assess potential outcomes for different regions of the world. These patterns are also informed by the planet’s geological records as there have been periods of similar temperature over the millennia.
What the world could look like
The greenhouse effect is a completely natural process and has been happening since the earth formed a planet. The planet has gone through periods of warmer weather after long ice ages for millions of years.
Just 50 million years ago, Earth had much higher levels of carbon dioxide and early mammals struggled to survive in a tropical atmosphere that engulfed the planet. Much of the carbon dioxide was absorbed when the Indian subcontinent finally met Asia and created the Himalayas which became a great carbon sink.
Once carbon levels were reduced, millions of years of ice ages followed, interrupted by periods of milder temperatures. About 3 million years ago we find a period when carbon dioxide levels were similar to present levels.
But we will not recognize the world where the deserts of Namibia and the Sahara were covered with savannah, woods and lakes and where giant animals still roamed.
The outline of the continents would be different because miles of today’s coastal areas are under seas nearly 30 meters higher than present levels. Not far from the South Pole trees exist, remnants of a forest of an even warmer age.
There are more recent examples dating back 120,000 to 20,000 years which are also instructive as to what might be happening.
Let’s talk about weather…
Weather is the local condition of the atmosphere at a specific time such as an hour, a day or a month. Climate change can affect local weather patterns, making regions on average hotter or colder, wetter or drier, more or less prone to storms than recent historical patterns.
Climate describes typical weather conditions at that time, year, or season for a specific region based on long-term trends and averages. The Western Cape is in a winter rainfall zone 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 the local weather will be affected by climate change, as this affects their planning and decisions.
In the next article, we will look at how agriculture both contributes to the greenhouse effect and mitigates its impact.
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