Just three months ago, I was a firm supporter of the idea of global warming caused by human activity. After all, it made perfect sense. Burning fossil fuels produced carbon dioxide, creating the greenhouse effect that heated up planet Earth. Most of the world’s leading climate scientists said this was so, and I believed they could not all be wrong.
Then, the Canadian winter happened. Temperatures plummeted to -27 C in the month of November, something I had never seen before. All of North America was caught in this deep freeze. It happened in India too, where low December temperatures in many parts of the country broke a 17-year record.
Statistically, a single weather event means very little. So, I looked at historical global temperature records for the last two decades on the NASA website. To my surprise, I found that the average global temperature for the last 17 years showed no significant warming trend. In fact, the global temperature in 2012 was lower than in 2002. This trend stretching over 17 years could not be dismissed as a single weather event.
Climate scientists at the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) are aware of this trend, which they often call a “pause” or “hiatus” in global temperature rise.
Some have tried to explain it by saying that the excess heat is being absorbed by the oceans and that the temperatures will rise again. Some point toward rising ocean levels as an indicator of global warming; however, sea levels have been rising gradually for at least 100 years, long before human activity produced significant amounts of greenhouse gases.
Some scientists have advanced the theory that natural weather cycles may have obscured the effects of man-made global warming. They point toward a 30-year cycle in ocean currents as the cause. All it really means is that, perhaps, natural weather cycles play a bigger role in global warming or cooling than was anticipated by the scientists.
How do the scientists know that global warming is happening? They base their predictions on computer models that simulate the effects of greenhouse gas “forcing” on global temperatures. These models were first developed about 20 years back, when Earth was in a warming phase. At that time, the results from the computer models matched historical data fairly well. This is no longer the case.
A recent study by some Canadian scientists offers a few clues on what is happening today. It was published in the Nature Climate Change journal in September 2013, titled “Overestimated global warming over the past 20 years.”
The study examined 117 different computer simulations from 37 climate change models in the Coupled Model Intercomparison Project. It found that, for the last 20 years, the computer models overestimated global warming by 50 percent.
For the last 15 years, the study noted that the global temperature trend was 0.05 C plus or minus 0.08 C per decade, not significantly different from zero, pointing toward a hiatus in global warming. At best, the actual temperature rise, if any, was four times smaller than what the computer models had predicted.
Scientist often use the term “climate change” rather than “global warming,” but the change of terminology simply confuses the issues. Climate change is harder to quantify than global warming, making it harder to link cause and effect. If there is a hurricane in the Philippines, how can we prove or disprove that it is linked to greenhouse gas emissions? If Hurricane Sandy strikes, is there a link to greenhouse gases?
On the other hand, it is easier to quantify global warming or cooling. All we need to observe is the average surface temperature over land or sea over a period of time. It is relatively easy to compare this with observed levels of carbon dioxide in the atmosphere to see if there is any correlation.
Regardless of whether the planet is warming up or cooling down, we need to reduce air and surface pollution. Air pollution is causing severe health problems in many parts of the world, including countries like India and China. Surface pollution is even worse, as the pollutants can stay on the ground for decades, seeping into the water systems.
Above all, we need to develop more clean, renewable sources of energy, as they cause the least amount of damage to the Earth we live on.
Niraj Chandra is a professional engineer and the author of a book on renewable energy.