In the late 1960s and early 1970s, computers advanced to the point of performing complex calculations in short timescales. Better observational data and measurements were made available through satellites and ground measurements. These conditions facilitated the emergence of three-dimensional atmospheric general circulation models, which represented climate as a comprehensive system. As they developed, general circulation models treated the atmosphere as layers and incorporated processes of convection, evaporation, and rainfall. The models could simulate the transfer of radiation vertically through the atmosphere, the reflectivity of sunlight from snow and ice, and basic seasonal changes. During this period, oceans were represented in models and coupled with the atmosphere, though these early models treated the ocean as a slab, without any unique dynamics of its own. General circulation models permitted analysis of how the movement of radiation through the atmosphere was affected by water vapor and CO2.
Throughout the 1970s, Syukuro Manabe built and enhanced a climate model to analyze the relationship between CO2 changes and climate change, a concept known as climate sensitivity. Specifically, the model investigated how a doubling of atmospheric CO2 concentration would change temperature. The first estimates indicated that temperature would increase by approximately 3.6 degrees F (2 degrees C). In this way, models raised awareness among the scientific community that rising CO2 in the atmosphere could lead to increases in the Earth's temperature, a phenomenon known as greenhouse warming.
By the 1980s, atmospheric general circulation models permitted analysis of climate component processes occurring on smaller spatial and temporal scales. Also, models of this period coupled the atmosphere and oceans in a complex way by simulating the exchange of heat between both components. Coupled models could simulate changes in sea ice, as well as the emergence of deserts and rainfall areas. As the use of coupled models advanced, research into atmospheric changes in CO2 revealed serious consequences for the processes driving the overturning of ocean waters, which could potentially cease with higher levels of CO2.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.