2011-07-18 07:02:19A Lousy Two Degrees - Who Cares?


Many people are quite sanguine about an increase in temperature of 2°C associated with climate change. Others positively welcome it, describing it and increased CO2 in the atmosphere as beneficial, even asserting that an increase of 3°C would be welcome and easily tolerated. If you live in Brisbane, Australia or Lisbon, Portugal, you may shrug your shoulders and say “So what? Another 2°C isn’t going to harm me. In fact it would be very welcome in winter”.


This suggests widespread misunderstanding of the warnings given us by climate scientists about the dangers posed by rising temperature. So let’s be clear. When they talk about the need to limit temperature increase to 2°C, they are talking about a rise in average global surface temperature compared to that prevailing prior to the Industrial Revolution or ~1750.


Average global temperature is what it says: the average of temperatures taken world-wide over a year. It must not be confused with the temperature at any one particular location or time which vary considerably depending on the season, unusual climate events and a lot of other things.


One of the things we know about global warming is that it is causing temperatures to rise world-wide but rise more rapidly in some areas than it does in others. For example in tropical-equatorial regions, say between 23°N and 23°S temperatures rise more slowly and to a lesser extent than they do in more temperate and cold regions between 23°-90°N and S.


In fact the further north or south of the equator you go, the greater the effect of global warming on air and sea temperatures. So an increase of 0.75°C in average temperature in the tropics may result in a temperature increase of ~1.5°C in more temperate regions such as southern Europe and be much higher in polar regions.


While the people of Brisbane may think little of a 1°C increase, the people of Toronto, Canada may find a 3-4°C increase a burden when added to the temperature of their hottest days of summer, particularly if those days are consecutive and numerous. Those living in the Arctic may find the effects of a 4-5°C increase in summer temperatures even harder to live with if it melts ice on which they rely.  Ask the Inuit, walruses and polar bears.


When average global temperatures increase by 2°-3°C, as they certainly will before 2100 if we do nothing to effectively reduce greenhouse gas emissions, temperatures in the tropics will not have changed much. However, more densely populated temperate regions of the world can expect to experience average temperature increases of up to 4-5°C. In polar regions temperatures may be 5°-7C warmer, significantly speeding-up ice melt and ocean warming.


Many people smile tolerantly at climate scientists who urgently warn of annual changes in temperature measuring 0.06°C. Miniscule! Who cares? Nobody notices such a small rise and very few understand why scientists get alarmed at these “huge” increases - even when they point out that they equate to average global temperatures rising over 5°C by 2100. In temperate regions that translates to an intolerable increase of 7-8°C or more and in polar regions in excess of that.


If global warming were a faster process, its effects on climate would be far more evident and alarming. Since 1900, average global temperature has risen by 0.75°C and is continuing to rise at an accelerating rate, very much faster in the last 30 years.


Effect on feedbacks

Of concern is that as temperature rises, it will cause an increase in the concentration of greenhouse gases in the atmosphere. That increase will cause even more greenhouse gases to enter the atmosphere, causing temperatures to rise even higher, and so on – the “feedback effect” particularly related to:


  • Thawing permafrost: causing organic material beneath the surface to resume decay and in the process release methane (CH4), into the atmosphere. CH4 is relatively short-lived but is a powerful greenhouse gas causing rapid temperature increase.


  • Thawing clathate:  an ice like substance beneath seabed silt in polar regions is beginning to melt.  In the Arctic it now releases >1 million tones of CH4 annually into the atmosphere and a greater amount of CO2.  Both contribute to the Arctic amplification.


  • Land warming: as land surfaces are warmed, particularly in temperate areas, they release CO2 absorbed by them in the cooler conditions that prevailed over past millennia.


  • Ocean warming: Oceans are the worlds’ largest CO2 sink.  As they get warmer two things occur, 1. their ability to continue absorbing CO2 is reduced and 2. warmer parts of the ocean may begin releasing CO2 into the atmosphere.


  • Evaporating water: as temperatures rise, the magnitude and rate of water evaporation from sea and land increases, as does the level of water vapour held in the atmosphere. Water vapour is the most powerful of greenhouse gases, causing prolonged and rapid increase in temperature.


  • Melting snow and ice: increases as temperature rises, exposing darker surfaces beneath for longer periods each year or completely. Snow and ice reflect solar energy back into space but when exposed, the darker surfaces beneath absorb solar energy contributing to a further rise in average global temperature.


Each of these feedbacks is initiated by rise in temperature caused by release of greenhouse gases arising from human activity.  Each contributes to a further increase in atmospheric temperature. While humans can directly control the level of greenhouse gases they emit into the atmosphere, they can do nothing to control or limit feedback effects they initiated.  Combined with anthropogenic emissions, feedback effects could increase average global temperature so much that abrupt climate change ensues.


Effects on the environment

Rising temperature has a number of destructive effects on the environment and the ability of animals to survive in it. Plants and animals have adapted over thousands of years to variable but very slowly changing conditions. Those conditions are now beginning to rapidly change, much quicker than some species can cope with.


Species that can not adapt to a changing environment will become extinct and there is ample evidence that this is already occurring because of the effects of global warming. Those effects include:


  • Damage to and destruction of buildings, roads, railways and reticulation built on ground softened by the melting of permafrost.
  • Heat and draught conditions becoming more prolonged, extensive and severe, resulting in fire destroying crops and habitat, rendering it unable to sustain flora and fauna.
  • Warming of surface sea water causing degradation and destruction of marine habitat, the death of corals and other marine species.
  • Changes in seawater chemistry reducing or preventing calcifying animals forming shells and plankton blooming due to the declining presence of calcium and iron.
  • Retreat of land based glaciers and snow cover reducing their ability to store and seasonally release sufficient water on which most species depend.
  • Warming of land surface causes evaporation of water content depriving food crops and other plants of essential moisture.
  • Loss or movement of species on which others depend for food or have a symbiotic relationship.
  • Melting of polar ice sheets and expansion of water resulting in sea levels rising, risking flooding and destruction of land based habitat.


All of these effects are now evident and, to varying degrees, are a cause for concern. Combined and if permitted to develop, they have the potential to threaten the ability of all life forms to survive on this planet. For this reason we should be concerned about global warming, the extent to which humans activity causes it and action which can and should be taken to limit if not control its effects.


We should be asking ourselves: Have we sown the seeds of our own destruction, what are we going to do about it and when?


Effects on humans

Russian President Putin once commented on the prospect of a 2°C increase in temperature: “Good news! We won’t have to spend so much on warm clothing”.  In summer 2010, the people of Moscow had to put up with heat wave conditions which took temperatures to over 35°C for over 2 weeks.


The death toll rose sharply. 50,000 premature deaths and destruction of >25% of the national grain crops were reported. Russian Premier Putin somberly committed to reduce greenhouse gases to 25 percent below 1990 levels by 2020.


The most obvious effect of weeks of summer temperatures exacerbated by global warming in temperate areas is that it causes premature death among humans and loss of food crops. 


Less obvious, though becoming increasingly evident, is that global warming now approaching 1°C, is responsible for the melting of most of the world’s glaciers. Until now, those glaciers have grown in winter, slowly shrinking in other seasons, releasing water into rivers and lakes on which humans rely for drinking water and agriculture.


Reduction in availability of surface water is forcing the pumping of aquifers at unsustainable rates and has curtailed food production in some otherwise fertile and productive areas. This is exacerbated by increased demand for food and water from a global population expected to exceed 10 billion before 2050.


The risk to food security is further exacerbated by the possibility arising from ocean acidification of a major break in the food chain for fish combined with degradation and loss of marine habitat. Pteropods on which many species depend for food are expected to be extinct by 2050.


The prospect of higher temperatures combined with higher humidity is particularly daunting. Humans and other species will find it difficult to deal with, not only because humidity limits our ability to cool by sweating, adversely affecting the young, aged and sick by causing hyperthermia which, if unrelieved, is always fatal.  Humans, even the fit and healthy, when exposed for more than a few hours to high humidity and air temperature in excess of 35C, will die.


Before 2050 is it likely that rising sea level accompanied by more frequent extreme climate events, such as storm surges and cyclones, already evident, will cause flooding of low lying coastal land. The latter will include river delta’s – highly productive agricultural areas, often densely populated.


Some 70 percent of humans live in or near the coast, many in cities such as Cairns and New Orleans which are particularly vulnerable to flooding from rising sea levels. The suburbs of many major cities (Sydney, New York, Antwerp, Shanghai etc) are also subject to flooding, destroying public assets and private property, disrupting if not preventing their ability to function.


The future

Based on current trajectories for human emission of CO2, the target of keeping temperature increase to 2°C will not be met by 2100. It is more likely that average global temperature will rise by 3.5°-4°C by the end of this century. In temperate and polar regions this equates to a rise of 7°-8°C and that has fatal consequences.


It spells more rapid melting of the Greenland and West Antarctic ice sheets, faster rising sea levels and an increasingly unstable climate that is too hot for comfort.


To avoid these outcomes it is not enough for a few countries to adopt emission reduction targets to limit global warming and assiduously work to achieve them. All countries must do so and bear in mind that by 2100 temperatures are not suddenly going to stop rising. By then they may be uncontrollable, unstoppable, unforgiving – and deadly.


A lousy 2 degrees – who cares?  We all should.  We are already heading for trouble. If business as usual remains accepted practice, we will, to use a technical term, be in deep shtuck.

2011-07-18 07:55:19


This essay was written in March 2011 for publication by On Line Opinion (OLO) and its broad (sometimes uninformed) readership.  It was rejected for publication by the OLO Editor (Graham Young) on the grounds that it contained a number of errors, most notably the assertion that humans could not survive a temperature of 35C and relative humidity >90%.  So, it may not be suitable for publication by SkS ??

Following rejection by OLO, I discussed the findings of Dr. Steve Sherwood (UNSW) with him and with medical doctors.  He was adamant that his findings were correct.  They had, after all, been peer-reviewed and published by a reputable journal.  Medicos I consulted confirmed his conclusions.  Graham Young still refused publication.

If the essay contains errors, please point them out and I will correct them.

2011-07-18 09:19:13
Dana Nuccitelli
Towards the end in 'the future' section I'd clarify that we can only limit global warming to 2C above pre-industrial with major emissions reductions. You can link to 'The Critical Decade Part 3' which I believe talks about what it will take to limit global warming to that level. Realistically, 2C is about the bare minimum we can limit global warming to at this point. Otherwise it looks good to me. I'm no doctor, so I can't comment on the health effects stuff.