The IPCC's conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue. The stated degree of confidence in the IPCC assessment is higher today than it was 10, or even 5 years ago, but uncertainty remains because of (1) the level of natural variability inherent in the climate system on time scales of decades to centuries, (2) the questionable ability of models to accurately simulate natural variability on those long time scales, and (3) the degree of confidence that can be placed on reconstructions of global mean temperature over the past millennium based on proxy evidence. Despite the uncertainties, there is general agreement that the observed warming is real and particularly strong within the past 20 years. Whether it is consistent with the change that would be expected in response to human activities is dependent upon what assumptions one makes about the time history of atmospheric concentrations of the various forcing agents, particularly aerosols.
While it is agreed upon that there is much uncertainty surrounding the Earth's climate, most scientists are in agreement that the last twenty years have produced "particularly strong" observed warming events. One could assume these events coincide with the industrial rising of countries such as India and China where carbon monoxide levels are increasing at a troubling rate. The United States and other countries are also responsible with more than 18% of CO2 emissions occurring from America. Although one could argue that Earth may be in a natural warming cycle, it is undeniable that pollutants released by humans are growing at a rate that will be unsustainable for the planet if allowed to continue.
Republican candidate Rick Perry has gone on the record stating he believes that global warming is a "hoax" and that the climate has been changing "ever since the Earth was formed". While true, Perry's response plays down the argument questioning the human aspect of the warming and seems to paint the issue as something fabricated by scientists eager to make a profit off the funding of new projects. Perry's chief rival for the nomination, Mitt Romney, has distanced himself from Perry's remarks by stating: "I believe the world is getting warmer, and I believe that humans have contributed to that".
Perry's stance is troubling because it conveys (in my opinion) a refusal to even consider the idea as plausible and downplays the idea that humans and Americans should consider what they can do to reduce global warming. For a moment, let's consider that Americans reduce greenhouse emissions and make painful lifestyle changes throughout the country that result in lost jobs, elimination of useful and effective products and an increased responsibility by every citizen to take ownership of the problem. If those such as Perry are correct and the Earth is in a natural warming state or not in one at all, then dollars and livelihoods will be affected and measures put in place will be for naught, ineffective or unnecessary. While unfortunate, those outcomes would hardly seem to be painful to swallow.
On the other hand if humans had the ability to take measures to stop the trend and do nothing, the outcomes would be painful and terrifying. Humans would watch as biological diversity slowly dies away and an increasing number of species become extinct due to inability to adapt to climate change. Sea creatures such as plankton, a nutrient source for many creatures, could be affecting by rising sea temperatures causing uncertainty over the survival of much aquatic life. Humans would cope with decreasing water supplies, proliferation of deserts and arid land and world-wide competitions for ownership of water and natural resources supplies. Rising sea levels would affect coastal communities and islands, forcing millions of people to relocate or risk being swallowed by the sea. In short, images from movies such as The Day After Tomorrow, while extreme, could become a reality for many populations throughout the world.
If the costs of being proactive are small compared to the risks of inaction, why aren't many humans concerned with global warming? Is it apathy, ignorance, conflicting beliefs or some other viewpoint that creates lack of action? For me, the risks of doing nothing far outweigh the costs of doing something. For those opposed to the idea of global warming, an eventual validation will lead to a brief "I told you so" moment and a platform for political maneuvering. A validation of global warming coupled with inaction could lead to annihilation and a plot line from Terra Nova becoming reality.