Global Warming. History and Causes of Global Warming

Global warming, also referred to as global change or climate change, is a topic frequently in the news. With reports of extreme weather events such as flooding, severe droughts, and storms, people have become more aware of the potential risks of global warming. Governments of the world have been under increased pressure to take action to reduce these risks. However, it seems that little progress has been made, despite scientific predictions, international protocols, and the desires of some decision makers and organizations to act.

Ecosystems, including humans, have always had to adapt to climate change as a natural phenomenon. The use of technologies and unsustainable practices such as a heavy reliance on fossil fuels, increased human consumption, and a growing world population have led to a crisis in terms of the influence of human activities on world climate.

Production of greenhouse gases, especially carbon dioxide (C0₂) and methane (CH₄), has reached levels never recorded before in the past 160,000 years. Most (76 percent) of this additional production comes from human use of fossil fuels in industrialized countries.

History and Causes of Global Warming. The connection between global warming and greenhouse gases, especially C0₂, is not a new concept. In fact, Jean Baptiste Joseph Fourier in 1824 was the first to suggest that the gases in the atmosphere serve as barriers for solar radiation escaping from the Earth and thus influence temperatures at the surface of the planet. In 1896 Svante Arrhenius formulated a theoretical model with C0₂ as the main greenhouse gas.

The principle is simple: The gas layered atmosphere serves as a barrier for solar radiation, keeping it trapped at the surface of the planet. The principle is referred to as the greenhouse effect. But only in the past thirty years have models been sophisticated enough to correctly link recent human activities and the use of fossil fuels to increased greenhouse gases and global warming.

Examining records from monitoring stations around the world, scientists from the Goddard Institute for Space Studies in the United States were able to demonstrate that the global temperature of the Earth has steadily increased over time.

The global mean temperature was 0.6° C warmer in the 1990s than in the 1890s. At the same time, they reported that not only was C0₂ increasing in the atmosphere but so were other greenhouse gases such as methane (CH₄), nitrous oxide (N₂0), chlorofluorocarbons (CFCs) and their substitutes, hydrofluorocarbons (HFCs) and hydro- chlorofluorocarbons (HCFCs). For example, CH₄ has increased by more than 145 percent in the atmosphere since the beginning of the industrial era.

Natural variation in greenhouse gases is common, and climate records, through analysis of ice cores, clearly show that mean temperatures and C0₂ levels in the atmosphere have been naturally varying over the past 400,000 years. These variations are normal and related to the changes in the inclination of the Earth and its orbit around the sun.

Recent data showed that for ten thousand years the concentration of CO₂ in the atmosphere was about 280 ppmv (parts per million in volume), lire concern comes from the rapid changes that have occurred over the past 120 years. Since the 1800s, with the use of coal and other fossil-fuel sources, the concentration had increased to about 368 ppmv by 2000. Whereas under natural conditions the atmosphere would contain approximately 750 billion metric tons of gaseous carbon, the current increase in C0₂ of about 0.4 percent per year can be translated into an additional input of 3 billion metric tons of C0₂ gas into the atmosphere per year.

Normally, under natural conditions, there would be a balance in the global carbon cycle. But deforestation, land degradation, and habitat loss have reduced the capacity of some ecosystems to absorb carbon. With greater gas emissions from anthropogenic activities, the short-term exchanges and reservoirs are unbalanced, leading to more input of greenhouse gases than sinks (a loss or a permanent reservoir such as trees).

The increase of C0₂ in the atmosphere is obviously caused by fossil-fuel consumption. Fossil fuel as a source of energy is readily available for most populations, and current technology makes it cheap. Although it is nonrenewable, its availability and the current reserve suggest that humans will rely on it for many more years.

Greenhouse emissions can be associated with many human activities; humans cause emission of C0₂ mainly by combustion of fossil fuels and deforestation. Fossil fuels include coal, petroleum, and natural gas and are mostly used for energy generation. In the United States, for example, the energy sector is one of the largest consumers of fossil fuels, producing 35 percent of all C0₂ emissions as well as 25 percent of all NO* (nitrogen oxides) emissions and almost 70 percent of S0₂ (sulphur dioxide) emissions. Cement manufacturing is also a huge contributor of greenhouse gas emissions at 3 percent.

The production of greenhouse gases from human activities is not similar among all countries. As would be expected, industrialized countries contribute at a greater rate than do developing countries. For example, in 1991 countries such as the United States and Australia emitted on average 4.7 metric tons of CO²- carbon per person per year, whereas countries such as Cambodia and Rwanda emitted 0.02 metric tons of C0²-carbon per person per year.

Deforestation, the other major cause of an increase in human-created greenhouse gas emissions, is a global phenomenon in which wood is harvested for various uses, such as fuel, construction material, or paper production. In developing countries, where the population is increasing rapidly, land is deforested for agricultural use. In many ways, carbon storage is positive as it helps reduce the amount of GHG in the atmosphere.

However it can take the planting of 140 trees to compensate the emissions of only one car. So yes, it is important, but we shouldn't, think that just by planting trees, we will reduce GHG emissions. The reason is that forests are part of the large sink for carbon accumulation. Ninety percent of the carbon stored on land is located in forests. Half of this amount is stored in tropical forests. In the past 130 years, deforestation has caused a decrease in carbon storage in forests by 38 percent.

Most of this decrease has come in tropical forests. But contrary to what is commonly believed, in the past fifty years northern regions of Europe and America have been able to increase their carbon storage by the regeneration of forests and tire abandonment of agriculture.

Current data show the important role that industrialized countries can play in reducing greenhouse gas emissions through changes in technology, energy sources, and socioeconomic behaviors. Their levels of emissions are such that without changes, it is difficult to see long-term reduction of greenhouse gases. With the accelerated economic growth of several developing countries it is predicted that the global levels of greenhouse gases will substantially increase.

Unless these countries implement important socioeconomic strategies, they Will experience situations similar to those in industrialized counties. Because these data can be controversial and can have incredible impacts on most countries, the challenge has been to have adequate and credible data and assessment to convince decision makers of the threat of global warming.