Earth is warming up but not as rapidly as predicted

New IPCC report raises questions over urgency or seriousness of climate change

Updated - December 04, 2021 11:21 pm IST

Published - September 05, 2013 02:04 am IST - NEW DELHI:

In this July 19, 2007 photo, an iceberg melts off Ammassalik Island in Eastern Greenland. In the last 15 years, the rate of warming has been 40% slower than in the period 1951-2012, according to UN’s IPCC report that is to be released in September this year.

In this July 19, 2007 photo, an iceberg melts off Ammassalik Island in Eastern Greenland. In the last 15 years, the rate of warming has been 40% slower than in the period 1951-2012, according to UN’s IPCC report that is to be released in September this year.

The climate has not been warming over the past 15 years at rates predicted earlier, the latest report of the U.N.’s Intergovernmental Panel on Climate Change (IPCC), to be released September end, is going to say.

The report is also going to accept that carbon dioxide gas concentration in atmosphere may not be as potent in causing global temperature increases as was believed earlier. The Hindu accessed the report’s Summary for Policy Makers — a precise guide for political leaders and negotiators on what the latest science of climate change is indicating.

The report says: “The rate of warming over the past 15 years (from 1998-2012) at 0.05 degree Celsius per decade is smaller than the trend over the longer period 1951-2012 which stands at 0.12 degree Celsius per decade.” This means that in the last 15 years, the rate of warming has been 40% slower than in the period 1951-2012.

But the facts do not take away from the reality of anthropogenic climate change. They instead suggest that the understanding of the emissions-temperatures-nature linkages is being revised and that the level of urgency or seriousness of the issue is being revisited by science as well as policymakers.

The IPCC is the apex body of the U.N., providing guidance to the countries on what is the best, the latest and the most authentic science available on climate change. The summary is in the form of a final draft, which is going to be fine-tuned by negotiators days before being released on September 27. But it is now almost certain that the sudden dip in global warming — often called the hiatus — is going to become the most controversial and key element of the report. The last time the IPCC brought out such studies in 2007 as part of the ‘4th Assessment Report’, it led to a high-pitched demand for greater action against climate change and consequently a high-profile meeting of the countries at Copenhagen in 2009.

This report and others to be produced by the IPCC through the next few months are going to form a critical input into the new global agreement that the world is supposed to finalise by 2015. But this report has brought back on top the question that a sluggish global economy is expected to push: is there really an emergency or has the latest science shown that countries may have more time at hand to sign the new agreement?

The report does not say the temperatures are not rising over the long run as emissions of greenhouse gases go up in the atmosphere but that the somewhat linear relation many presumed up to now about the two may not be true. The long-term trend though is rather clear as per the report. Various reasons are provided for why it may be so. The report, however, does say that each decade has been warmer than all preceding decades since 1850 and the first decade of the 21st century has been the warmest.

But the nature of international political processes that come together at the UN climate negotiations and the general economic lull is expected to play up the hiatus. At the last Major Economies Forum meeting recently and before that too some countries had hinted that 2015 may not be the year that the new agreement is all completely sealed up. They suggested that large and critical elements may be agreed upon by 2015 and the details of how countries would really act could flow in later by the time the agreement gets operationalised in 2020. The report on the hiatus and warming impact of CO emissions could further compound the reticence of many countries.

The report predicts that by the turn of the century, the temperatures are likely to exceed 1.5° above pre-industrial era. The chances that the temperatures will go beyond 2° above the pre-industrial era are less likely under most scenarios. Temperatures shooting more than 4 degree higher above the benchmark are rather unlikely.

Because these predictions are probabilistic in nature, terms such as ‘likely’ or ‘very likely’ refer to a range of probability that an ‘event’ may take place.

Another controversy has been finally addressed in the UN’s IPCC report — how strong is the impact of carbon dioxide emissions on the atmosphere in raising the global temperatures. The new report has brought down the lower range of the impact of the gas concentrations by a substantial level. This impact is measured by predicting how much the global mean surface temperatures would change after the concentration of the gas (in this case CO) is doubled in the atmosphere and the natural systems allowed to reach a new equilibrium. Earlier the IPCC said the likely range of increase would be 2° Celsius to 4.5° Celsius. The new report says with high confidence scientists conclude the doubling of CO emissions could have as low an increase in global temperatures as 1.5°.

This again leads some to say that the fear that the world may be staring at an immediate crisis could be exaggerated and the global community could have just a bit more time at hand than it has been presumed earlier. But many do contend that the slow pace of negotiations and the effort being made are already too little to check climate change impacts.

The science reproduced in the IPCC reports is the latest research gathered over the past few years by a large panel of scientists. The IPCC had earlier come in for criticism for letting less than well established facts creep in and the climate sceptics have always blamed it for pushing the reports beyond legitimate limits and ignoring contrary scientific signals. The new report does take a more ‘moderate’ view on some impacts and scientific facts related to science but continues to be unequivocal, and in fact more confident, that global warming is hastening even though there might be some vagueness about how the warming will alter natural processes, especially at regional and local levels.

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