It looks like watching just global temperature may mask the real malady, says S.Ananthanarayanan.
Since a decade, the world has been kept in mind a target of containing the rise in global temperature to 2°C .There is a general understanding, at least in principle, that our way of living, consuming electricity generated by burning coal, burning petrol, using plastics, the rise in population, are filling the atmosphere with greenhouse gases, and the globe is warming. The figure of 2°C has been put out as a responsible, which is to say, practical and adequate, limit to the warming,which we must enforce, but there is less clear understanding of how this can come about.
David G Victor and Charles F Kennel, respectively professor at the School for International Relations and Pacific Studies and distinguished professor and Director emeritus at the Scripps Institution for Oceanography, both of the University of California, San Diego, in a Comment published in the journal, Nature, raise serious questions and warn of the dangers of putting this number, 2°C, into the minds of the public and leaders of nations.
The sea absorbs heat
An important point the authors make is that while the rise in global temperature refers to the average surface temperature, the real harm to planet earth is the rise in total heat content of the earth, which arises because of more absorption of heat than reflection and radiation. The authors note that while heat content has been steadily rising, the surface temperature has remained almost unchanged for the last sixteen years. But how could be it that heat content is going up but the temperature does not? The answer lies in the role of the sea, which is taking up the heat and circulating it out of sight for some time, the authors say.
The total mass of water in the oceans, which cover 71% of the earth’s surface, is around1.3 billion cubic kilometers. A cubic meter of just water, without the saline content, weighs a tonne. A cubic km weighs a billion tonnes. The water in the oceans then weighs 1.3 billion times as much. The mass of the atmosphere, in comparison, is about 5 billion times a billion kg (not tonnes), which is to say that the water in the oceans weighs about 250 times more than the atmosphere. The next thing about water is that it has great heat capacity. Heat capacity is how much heat it takes to raise the temperature of 1 kg of water by 1°C. It turns out that the heat it takes for a kg of water is four times what it takes for a kg of air. As the oceans weigh about 250 times the atmosphere, the oceans can absorb heat about a thousand times more effectively than the atmosphere. Water, in fact, has almost the highest heat capacity of ordinary substances, over ten times that of most metals, for instance, and it is not far wrong to say that the total heat capacity of the oceans is a thousand times that of the atmosphere and the outer land mass of the earth too.
Now, how about the temperature of the oceans? Well, the surface gets warmed by the sun and would stay at the top, but the wind and waves mix up the top layer, at least. And this warming depends on the latitude. The surface water keeps getting colder as one approaches the poles, and can be as cold as -2°C, with the formation of sea ice. Till the temperature drops to 4°C, in fact, the cold water sinks to the bottom and creates an underwater current that flows towards the equator. The result is that apart from the surface layer at lower altitudes, the sea is a pretty cold place. The average temperature at the surface is 17°C, but 90% of the volume of the sea is in deeper water, where the temperature is as low as 0-3°C.
Warming at the surface, as a result of global warming, thus, must percolate down to the ocean, and we have seen that the ocean has a thousand times the capacity of the atmosphere to absorb heat. This appears to be the mechanism that has set in, to stall the rise in global temperature in recent years. And this, David Victor and Charles Kennel say, is why the surface temperature is not a good indicator of the health of the planet. While it is one indicator, there are many others, the main one being the levels of CO2 in the air. The temperature in the sea, warming at the poles and melting of polar ice, changing weather conditions, changes in vegetation and animal population, are among other indicators.
Global temperatures give an impression of having stabilized because much of the heat is getting taken up by the sea. But the heat is not sequestered or locked away, as happens when plants grow, which is a form of cooling, but the heat is still there, to be released over centuries, and delay return to normalcy even if the greenhouse effect is controlled. Just watching the earth’s surface temperature would be misleading. It is important to monitor a range of indicators, like a physician relies on all ‘vital signs’ - blood pressure, blood and urine tests, electrolytes, the heart rate, and not only the clinical thermometer.
Apart from not being the right indicator from the point of view of science, Victor and Kennel say, setting a target in terms of limit to temperature rise is also not specific in terms of actions that world governments need to urgently take. Not setting down goals in terms of specific action, which can be planned and monitored, has been the problem with dealing with global warming since the beginning, the authors say. Even in 1992, the UN Framework Convention on Climate Change (UNFCC) expressed the objective as preventing “dangerous anthropogenic interference in the climate system.” Setting down an objective as broad as this leads to no coordinated, concerted and effective action by all or any of the signatories – as even science cannot specify what interference is dangerous, many answers being possible, according to what part of the climate system is being looked at and again, from what perspective. This is unlike other areas of international cooperation, where “goals have had a big effect when they have been translated into concrete, achievable actions,” the authors say.
Global action, if any has been taken, has thus been without direction, and the persistence of the target of ‘within 2°C’ has taken the spotlight away from more meaningful goals, like capping CO2 emissions, which have been articulated in later international conventions. “Because it sounds firm and concerns future warming, the 2°C target has allowed politicians to pretend that they are organiz¬ing for action when, in fact, most have done little”, the authors say. The 2°C target, despite theoretical models, is unattainable in practice and with growing emissions the world over, is sure to be passed before long, they say. But the comfort of the target is drawing attention away from urgent action that nations need to take to cope with the inevitable, they add.
Right now is the time and an opportunity, the paper says, as Governments prepare for refining the content of the new global agreement to be entered into at the UNFCCC meet in late 2015.” Getting serious about climate change requires wrangling about the cost of emis¬sions goals, sharing the burdens and drawing up international funding mechanisms. But diplomats must move beyond the 2 °C goal. Scientists must help them to understand why, and what should replace it,” the paper says.
The exercise to redefine the objectives of world action has commenced. An conference of the International Alliance of Research Universities, with delegates from Europe, USA, China, Australia,and other countries is taking place at the University of Copenhagen during 22-24 Oct 2014 to discuss the role of academia and research in guiding policy. The Climate Commissioner of the European Union is taking part and the outcome would be presented to Governments to take into account while finalizing their stand in the world conference on Global Warming, in late 2015.
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