A disagreement of the nature, the causes and the consequences of global warming.
Today, there is general scientific consensus that global warming is occurring and is primarily caused by human activities such as the burning of fuel and deforestation. More than 50 scientific societies and associations worldwide have publically supported the conclusions of the IPCC (Intergovernmental Panel on Climate Change) that climate change is anthropogenic and that action needs to be taken to reduce greenhouse gas emissions and to mitigate the impacts of climate change.
A 2004 study in the high ranking scientific journal Science found that virtually all studies published in scientific journals on the topic of climate change agreed with the scientific consensus, although predictions of the consequences of climate change showed some variation based on the climate models used.
However, there are some scientists that disagree with the IPCC and claim that the lack of disagreement in the scientific literature is because papers with other conclusions are rejected for political reasons and that scientist with divergent views are being ridiculed and keep a low profile for fear of losing their jobs.
In 2008, the Heartland Institute – an American libertarian/conservative think tank – revealed a list of 500 scientists who doubt that climate change is caused by man. However, it later emerged that many of the scientists were not directly involved with climate research and that another 45 scientists were included on the list without their consent and without them agreeing with the statement. Several other petitions from scientists against the findings of the IPCC suffer from similar problems.
There is, however, more serious criticism of the IPCC conclusions from scientists involved with the IPCC. The main critique is that the IPCC is too political and sometimes suppresses scientific evidence. However, none of these claims have yet been proven and they, furthermore, go both ways. Some scientists think that the IPCC over-estimates the importance of global warming, while others think that the IPCC, in order to achieve consensus, have too conservative views on the consequences of global warming.
Other climate sceptics, such as the Danish political scientist Bjørn Lomborg, agree that climate change is caused by humans, but disagree about the severity of the consequences and instead believe that the huge amount of money needed to reduce greenhouse gas emissions and combat climate change can be much better spend in other areas such as on hospitals and schools.
While the scientific consensus is that global warming is anthropogenic and caused by the emission of greenhouse gases such as CO2, climate skeptics have proposed alternative hypotheses. These include that temperature increase is caused by natural cycles, such as the ocean currents, solar activity and cosmic rays.
Some skeptics also question whether the recorded global warming even exist in reality or if it just due to errors in measurement. For instance, because cities are growing, many more temperature measurement stations are now located near cities, which are warmer than the surrounding landscape because of the urban heat island effect.