The Earth’s climate has been around for a very long time. Scientists have named the different periods of time during which the climate has been evolving. Let’s first consider this question; What is climate? Here is an interesting quote to start with; “Climate tells you what clothes to buy, weather tells you what clothes to wear”. The quote brings out a distinction between “Weather” and “Climate”. Weather is the state of the atmosphere at a particular place and time as regards heat, cloudiness, sunshine, wind or rain. Climate is the long-term regional or global average of temperature, humidity and rainfall partners over seasons, years or decades.
Whereas weather can change in just a few hours, climate changes over longer timeframes. Accordingly, The World Meteorological Organization defines climate as the “Average Weather” or the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands of years.
Research spearheaded by Dr. Scotese of the University of Texas has projected backwards the Earth’s climate about 2 billion years ago. The research reveals the Earth’s climate as alternating between the “Greenhouse period” characterized by a lot of more liquid water on the planet and the “Icehouse period” where the climate is cold enough to support solidified water i.e. Ice. One of the parameters used by the research in determining past climate is the type of Rock deposits and distribution of Animals and Plants. For instance, Coal deposits are associated with wet conditions like in tropical rain forest or temperate forests. Animals like Alligators and Plants like Palm Trees and Mangrove swamps are sensitive to climate and their distribution suggests the past climate conditions.
Our climate system is the result of a delicate energy balance and redistribution of the Sun’s energy on the surface of the globe. The redistribution of the Sun’s energy [as the Earth spins] results in the following climate conditions: warm near the Equator and cool near the two Poles; wetness and rainfall varying systematically from the Equator to the Poles – being wet near the Equator, dry in the sub-tropics, wet in the temperate belts and dry near the Poles.
Apart from the Sun’s energy redistribution on the Earth’s surface being a contributor to the climate system, the delicate balance of the incoming and outgoing Sun’s energy on the Earth plays an important role in shaping the climate system. The temperature on Earth is a result of the balance between energy coming into the Earth from the Sun [Solar Radiation] and the energy leaving the Earth into outer space.
About half of the incoming solar radiation is absorbed in the surface. The other half is absorbed by the atmosphere or reflected back into space by Clouds, Snow, Ice and Deserts at the Earth’s surface. The temperature we feel is the heat energy that is trapped on the Earth by the Earth atmosphere. According to the National Geographic, an organization based in the USA, the atmosphere which is composed of about 78% Nitrogen, 21% Oxygen and 1% other gases, protects life on Earth by shielding it from the incoming Sun’s radiation. The atmosphere acts as an insulator to moderate temperature.
This thermal retention is a naturally occurring “greenhouse effect” which has made the Earth habitable with an average temperature on Earth of around 14 degree centigrade. This natural “greenhouse effect” works by reflecting back to the Earth’s surface the thermal radiation by the atmospheric gas molecules and clouds.
However, more gas molecules are entering the atmosphere due to human activities and causing the trapping of more heat beyond what would have been trapped naturally. The time period of the dramatic increase in human activities affecting the Earth, which is assumed to have began around 1950, is referred to as “Anthropocene”. This is creating gradual increase in temperature and changes in climate.
Executive Director
May 21, 2023
