Global warming: caused by humans or not?

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Global warming: caused by humans or not?

Introduction

According to the Intergovernmental Panel on Global Climate Change (IPCC, its acronym in English) global warming is unequivocal and there are more than 90% of scientific certainty that changes in climate are intensified by human activities. To reach this conclusion, the IPCC has evaluated 577 scientific papers, describing 80 thousand sets of data, which show significant changes as retreat of glaciers, changes in volumes of water in rivers, lakes and oceans. Just as change in behavior of fish, birds, mammals and other animal species and plant species. According to several studies, the average temperature on Earth has risen by about 0.7 º C over the 20th century, and this warming is occurring more rapidly in the last 25 years (Godrej, 2001). The temperature rose to four times faster than the average since 1850. It is interesting to note that both natural causes such as those attributed to human activities are included in the models used by scientists to reproduce, in general, the curve of temperature evolution of the 20th century. It was found that the forcing anthropogenic is the dominant factor in the years 1970-2000 (Gore, 2006).

This information is the result of developments in the science of global warming, which has grown significantly in the past 20 years. Thus the projections of climate change are increasingly leaving the land speculation. Currently, the IPCC works with several models that attempt to explain the evolution of the climate of the Earth system (past and present), and a scenario in which the simulations for the future have higher reliability. However it is important to understand that the projections of climate models have many limitations, which should not be an impediment to decision making and implementation of measures to mitigate the effects of climate change. At this post-industrial age, human activity is the major cause of highly observed global warming (Godrej, 2001).

Evidence of Global Warming

The main evidence for global warming comes from temperature measurements from weather stations across the globe since 1860. The data with the correction of the effects of “urban islands” shows that the average temperature increase was 0.6 ± 0.2 º C during the twentieth century. The largest increases were in two periods: from 1910 to 1945 and from 1976 to 2000. From 1945 to 1976, there was a cooling that caused temporarily scientific community suspected that he was experiencing a global cooling (Gore, 2006).

The heating was not checked globally uniform. During the last decades, it was generally higher between latitudes 40 ° N and 70 ° N, although in some areas such as the North Atlantic Ocean, there has been cooling. It is very likely that the continents have warmed more than the oceans. There are however be noted that some studies seem to indicate that variation in solar radiation may have contributed by about 45-50% for global warming occurring between 1900 and 2000 (Williams, 2006, pp.32-55). Secondary evidence is obtained by observing the ...