The Origin: In the 1970s, an economist and professor of Yale, named William Nordhaus, was the first to theorize that warming of global temperatures more than 2°C, as compared to the pre-industrial era could cause the climate to dangerously move into limits that humans were completely unfamiliar with, essentially changing the world as we know it. However, this theory was not seen to be important at the time.
Further Research: It wasn't until more than a decade later, in 1988, when a professor at NASA, named Jim Hansen, spoke in front of US Congress about the link between man-made gas emissions and global warming. Although he did not specify exactly what dangerous climate change was, he was the first scientist to bring out the issue into the open to the public. Following on his work, a group of scientists at the Stockholm Environment Institute worked to find out the exact parameters for dangers in global warming. They found that, changes of over 1°C could cause fast and unpredictable changes in global weather, causing lots of damage to several ecosystems. However, to avoid the worst impacts, it was necessary to set a maximum limit of 2 degrees. These findings were largely responsible for the topic of global warming to appear in mainstream international politics, leading to agreements such as the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Copenhagen Accord.
With the heads of governments of over 120 nations coming together, the December 2009 Climate Change Summit at Copenhagen was the largest meeting of world leaders in history. At the conference, prime ministers and presidents of nations who contributed to more than 80% of the world's pollution debated and discussed the agreement, named the Copenhagen Accord.
Provisions: Under this agreement, the developing and developed nations agreed for the first time to reduce greenhouse emissions, and to register accurate commitments of efforts to be taken by individual countries by the start of 2010. It was an important first step in lowering emissions and creating a low-carbon global economy. However, despite high expectations from the public and pressure from the media, the nations could not agree on a deal on limiting global climate change to 2 degree Celsius over the pre-industrial average, nor was the agreement legally binding. It took another year for the 2 degree limit to be formally introduced in international policies, during the signing of the Cancun agreements of 2010.
As of now, various nations have made little progress towards this goal, and there are many questions about whether they will be able to stick to the target, and what can be expected if they fail. It is hoped that the new global climate deal of Paris, to be signed in December 2015, will be much more effective.
Researchers think that the impacts of climate change are going to get worse with the passing of time, and that the longer the delay is made to cut emissions, the more difficult it will be to meet preventive goals. Although climate change is dependent on many factors, its science is very complex, and as such, confuses and slows down the decisions made by politicians responsible for working on the solutions. In such a situation, the 2 degree target helps policy making, as it is very easy to understand and communicate. There is, however, another important question, which is whether this threshold is truly adequate and practical.
A New Target: Although the 2°C target had been officially endorsed as scientifically sound and justified in the Copenhagen Accord, the discussions that have taken place in the United Nations Framework Convention on Climate Change in December 2014 criticized the old estimates, and concluded that the two degree temperature rise had higher risks and impacts on global political power for developing nations than developed ones. Also, this target had increased risks of rainfall scattering, rising of sea levels, floods, droughts, and heat waves, than previously estimated. Over 70% of the representatives at the convention insisted that a long-term goal should be to keep the global temperature changes below 1.5°C, which is estimated to reduce the adverse effects of global warming by more than half, as compared to the 2°C target. Although this new target is still being reviewed, there are no clear indications towards making such a change a reality.
Other Limitations: Another important factor to consider is that, although using a figure for average global warming is convenient and compelling, it poorly represents the local climates across different regions of the world. Humans and various biological species across the world face different climates, and small temperature changes in the average global temperature has large-scale effects on localized biology. As such, it is important that a limit below 1°C is achieved and stabilized by the year 2100, as failure to do so can be catastrophic, and lead to increases of more than 4°C, at which point all bets are off.
The Stark Reality: Despite all the debates by the nations of the world, working on setting lower temperature targets might already be too late, as previous estimates on the effects of climate change at 2°C are already being seen at 1°C. Estimates by researchers around the world say that, considering the present world economy, climate, and the short time left before the world temperature rises by 2°C, a 3.5 to 4°C change looks highly likely by 2060, regardless of the preventive measures taken.
Heavy Emission Cuts: If the countries of the world had gotten their act together around 10 years ago, it would have been comparatively easier to model a path and achieve the 2°C target. However, due to the massive delays and procrastinations, unprecedented efforts need to be taken now collectively by all nations. Emission cuts will have to be 3 times that of the brutal 2008 financial crisis, when factories and pollution producing buildings were idling across the world, and these cuts would have to be continued year after year. Obviously, maintaining economic growth with such cuts is nearly impossible, and hence unfeasible.
Alternative Energy: Another alternative is that, all nations put every possible resource to massively increase alternative energy infrastructure for solar and wind power, and push on research to curb emissions from coal plants on a gigantic scale. Most importantly, we would have to invent certain technologies to pull carbon dioxide from the atmosphere on a large-scale. If such a milestone is achieved, economic growth rates would not be affected too much. However, such a project requires immense political will, investment, and global sharing of technologies, which all have their own obstacles to implement.
Despite the dire situation that we might find ourselves in, each one of us has to unceasingly work towards obtaining a sustainable planet, no matter what obstacles we might face. Apart from the governments of the world, it is necessary that corporate companies and individuals take responsibility and do their bit. It is pretty clear that we will have to change a lot more than just politics, before we can decisively change the world for the better, and help humanity to live a good life, instead of struggling to survive going into the next century.