Global warming and resulting climate changes were mentioned in the previous article “climate is changing”, nevertheless we need to clarify the term global warming first to understand the subject well then start to unveil its consequences.
The story start when sun light (radiation) reach the atmosphere, some of it is reflected directly in to space and the remaining portion goes through and reaches the surface of earth. The radiation hit the earth so part of it is reflected and the rest is absorbed by physical bodies which make gain energy (warm up). As we all know, warm body will be cooling gradually when we remove the source of heat (the sun in our case), the major mechanism that earth use to cool down is long wave radiation (heat). Long waves happened to be the radiation wave length that global warming gases have the ability to interact and absorb; this fact allow the atmosphere to hold on heat radiated back by earth for more time and made earth habitable for human kind (figure 1). The amount of heat trapped in the atmosphere by global warming gases increase when their amount increase in the atmosphere and that is what we call global warming and it is the major stimulator for the climate changes we live in our current times.
Figure 1: Greenhouse effect resulting from Global warming gases presence in the atmosphere
Climate change includes changes in the pattern and timing of weather events through time and will have varying effects on the regional and global level; however similar changes happened in the past but with totally different time scale. Earth’s climate has altered through the five billion years of its age, yet the changes took place throughout thousands of years and in slow pattern due to changes in the relations, interactions and effects between radiation from the sun, earth orbiting pattern and the state of land, oceans and atmosphere. The climate of earth fluctuated through the last five billion years between two cold and warm states known as the Ice House and Hot House respectively (figure 2). The Ice House state included Glacial and Interglacial periods (figure 3) in which Ice covered earth from the poles and varied in extent according to prevailing temperature. Ice covered large proportion of earth starting from the poles in Glacial periods.
Figure 2: Illustration of the changing climate million years ago and shows the Ice House and Hot House state
The current Interglacial period we live in started before 8000 years ago. However, the start of agriculture was known in Levant 2000 years before that, but the gradual rise in temperature followed, the stable CO2 concentrations and the climate stability at that times allowed human beings to farm lands and domesticate animals in an unprecedented extent. What is important to know is that the agricultural development mentioned before marked the start of human being civilization and can be traced to indicate the first effect of humans on the climate system through changing landscapes, natural habitats and land uses on earth.
Figure 3: Illustration of the changing climate thousands years ago and shows the Glacial and Interglacial periods
The climate change term is used recently to indicate for the altered climate we live as a result of increased global warming gases in the atmosphere elevating global temperature and changing the pattern and intensity of weather events that resulted in many effects on humans. These effects will be discussed in the future.
It is clear now that earth’s climate fluctuated naturally but the human being recently started to push the system towards unprecedented rate of rise in temperature, a case earth never have been before, and the major challenge we (all living creatures) face is to adapt with this wild change.
By: Hussien Al-Kisswani
Climate Reality project