Global cooling is the gradual decrease in the Earth’s overall temperature. It has been argued that global cooling is taking place since 1950, although some evidence suggests that it began as early as the 1940s. Global cooling occurs when the sun’s output decreases and/or when more reflective particles are ejected into space. The most likely cause of recent global cooling is a decrease in solar activity, which has been well-documented over the past few decades.
Solar activity varies on an 11-year cycle, and it is currently at its lowest point since accurate records began in 1868. This lull in solar activity could be responsible for a 0.3 ˚C drop in average global temperatures over the past century. However, other factors such as greenhouse gases and aerosol clouds have also been proposed as potential causes of global cooling. Greenhouse gases trap heat within the atmosphere, preventing it from escaping into space. This process warms the Earth and helps to offset any cooling that might occur from decreased solar activity or increased reflectivity of particles in space. Consol clouds are man-made aerosols that reflect sunlight back into space, helping to cool the Earth’s surface by reflecting some of the sun’s energy back out into space before it can reach and warm the ground.
It is still unclear how much each of these factors contributes to global temperature change. However, there is evidence that all three are playing a role in recent years’ cooler temperatures. The last time Earth experienced sustained global cooling was during what is known as the Little Ice Age, which lasted from approximately 1300 to 1870 AD. During this period, Europe and North America were particularly affected by cooler temperatures and advancing glaciers. If current trends continue, we may be headed for another Little Ice Age within our lifetimes