Weather is the elements we experience daily such as temperature, rain and wind. These elements change daily and sometimes hourly. Climate however, speaks of weather over a long period of time, typically around 30 years. Close observation and measurements have been used to establish climate zones across the world. Nigeria has a tropic climate that is relatively hot and dry. Climate can be described as a system containing a series of components that interact with one another, in relation with feedback mechanisms that facilitate self-regulation.
The greenhouse effect is basic to understanding what keeps our planet warm. Planet Earth receives incoming heat radiation from the sun that passes through the atmosphere. Some of the incoming radiation is absorbed by the diverse surfaces of the earth. For instance, the ocean, plants and soil absorb and re-emit heat radiation at long wavelengths that are invisible to us. The heat radiation coming off earth surfaces tries to escape to space, and some of that heat is trapped on the way out by the atmosphere, but only a little bit. What helps keep the Earth warm is the manifestations of some sort of gases in the atmosphere that absorb heat radiation and re-emit some of it back down to the earth’s surface in the form of infrared heat. These gases are known as greenhouse gases, and the phenomenon is called the greenhouse effect. These gases function more like a blanket around the planet, required to balance incoming and outgoing heat radiation.
The balance is meant to be achieved through a process – as radiation comes through the Earth’s atmosphere, some is reflected by clouds and scattered by particles in the atmosphere, while some is absorbed by ozone and other gases, but the remainder reaches the Earth’s surface. On the surface, some are absorbed and the rest is reflected back through the atmosphere to the space. The fraction that is reflected depends on the nature of the Earth’s surface and is called the albedo. Some surfaces like ice and snow reflect a lot of radiation. They have high albedo. Other surfaces like the ocean absorb a lot of radiation. They have low albedo.
Overall, the Earth reflects about 30 per cent of the sunlight that reaches it from space. In other words, it has an albedo of around 0.3. The 70 per cent absorption alone is insufficient for the required earth temperature. Without the heat generated from the reflection of radiation, the earth would be freezing. Earth would have an average temperature of 18 degrees centigrade below zero. The earth has the blanket of gases in its atmosphere to thank for warming the surface by 33 degrees to a comfortable average temperature of 16 degrees centigrade.
The consequential gases are carbon dioxide, water vapour, methane, ozone, and nitrous oxide, chlorofluorocarbons with water vapour being the most abundant and important.
Water vapour increases in response to increase in Earth’s atmospheric warmth, while carbon dioxide is released through natural processes such as respiration and through human activities such as deforestation and burning fossil fuels. Humans have increased atmospheric carbon dioxide concentration by a third since the Industrial Revolution began. Methane is produced from the decomposition of wastes in landfills and agriculture, while nitrous oxide is produced by soil cultivation practices, particularly when commercial and organic fertilisers are used, other sources are fossil fuel combustion, nitric acid production and biomass burning. Lastly, CFCs are entirely of industrial origin and they particularly contribute to the destruction of the ozone layer, which contributes to global warming.
Most climate science scholars, at one time or the other have concluded that the primary reason for the observed global warming is human activities that populate greenhouse gases. The last century witnessed massive burning of fossil fuels such as oil and coal, which has increased the population of atmospheric carbon dioxide. Oil or coal burning combines the escaped carbon with oxygen in the air to make carbon dioxide. In addition, greenhouse gases’ concentration has also been increased through land clearing for agriculture, industry and other human activities.
The Intergovernmental Panel on Climate Change is a collection of 1,300 scientists from many countries all over the world, gathered by the United Nations to access and review facts and figures of climate change. And they collectively concluded that there’s more than 90 per cent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide caused most of the observed increase in Earth’s temperatures over the past 50 years. The consequences of increasing natural atmospheric greenhouse effect are: warmer Earth, some regions will become wetter and others, dryer.
The sun also drives the climate. Sunlight provides energy which heats the Earth. The atmosphere stops the heat from escaping into space. The GHGs allow the sun’s energy through but stop it from escaping back into space. However, it is reported that since 1978, satellite instruments have been employed to measure the energy output of the sun directly. Data obtained show a very slight drop in solar irradiance (amount of energy the sun gives off) over this time period, implying that the sun is not responsible for the warming trend observed over the past 37 years. Also, there are proxy indicators that affirmed that solar irradiance changes cannot plausibly account for more than 10 per cent of the 20th century’s warming.
Understanding that planet Earth is a system such as a human body is key to acknowledging the possibility and existence of climate change. As the human body gets heated up as a result of fever caused by disease causing organisms, so does the Earth gets heated up (global warming) as a result of excess heat trapped by the greenhouse gases. Likewise, as antibodies help the human body reduce the population of disease causing organisms and in turn reduce fever, so does water, carbon, nitrate cycles and the likes help the Earth reduce the concentration of greenhouse gases and accordingly reduce global warming. The problem is not the greenhouse gases that trap sufficient heat to keep the Earth warm, but excessive population thereof, that traps excessive heat that do more than warming, but heat up the Earth and the planet seek balance by heat redistribution. The excessively trapped heat is not evenly distributed across the earth’s surface – some regions receive too little heat, while some others receive too much. Either way it is, it causes heat stresses and creates natural disasters such as wild fire in a place and flooding in the order. Lastly, as humans require more medicine and less poison to recover from fever, the Earth requires more oxygen and less carbon dioxide. Increasing vegetative cover, using less electricity, and recycling can help, among many others.
Ademola contributed this piece from Lagos via email@example.com