defining climate change terms

8/3/2019 Defining Climate Change Terms

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Defining climate change terms by Milan on March 23, 2010

in Climate change ,Climate science ,Ethics

It is important to avoid carelessly lumping together things that are very different,especially in the language we use to discuss climate change. Likewise, it is important toavoid using the same term to mean different things. How then should we understand theterms dangerous, catastrophic, and runaway in relation to climate change? Each termshould have a definition which is clear and comprehensible, and which does notobviously overlap with the definition of the others. That allows people to discuss thedifferent levels without excess confusion about what people mean by things.

As human beings burn fossil fuels and otherwise tinker with the planets carbon cycle, we

produce an increasing amount of climate change. The extent of this change can bedescribed as happening at different levels, either numerically or descriptively. This can bedone in several technical ways. * While these are useful, I think there are three descriptiveterms that are among the most useful, for distinguishing between future scenarios. Theyare defined not in relation to one number or another, but in terms of their overall effect onhumanity and the Earth:

Dangerous climate change

Bad as it would be, this is the least serious level of warming I will define. Of course, your definition of dangerous depends on your interests and situation. Climate change is

already dangerous for polar bears , Bangladesh, and small island states .

For this term, I will adopt the definition that has become common among scientists and policy-makers: a mean temperature increase of more than 2C, compared with pre-industrial temperatures. Basically, a world 2C hotter than the one that existed before westarted seriously burning fossil fuels.

Note that we have already created 0.74C of warming, according to the FourthAssessment Report of the IPCC, and that some additional warming is inevitable onaccount of the greenhouse gases we have already emitted. This term already hasimportance in international law. The objective of the United Nations Framework

Convention on Climate Change (UNFCCC), which the Kyoto Protocol extended, is toprevent dangerous anthropogenic interference with the climate system.

Catastrophic climate change

I define this as warming at such a level that it threatens the continued existence of humancivilization, for instance by radically altering regional weather patterns and puttingmassive strain on agricultural systems.
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The exact temperature level at which this would occur is impossible to know for certainin advance, but I dont think it is implausible to put warming of more than 4C to 5C inthis category. There is a plausible case that the relatively stable climate of the Holocene was one major reason for the emergence of agriculture and civilization as we know it. Asufficient level of climatic disruption could put that in jeopardy.

Runaway climate change

This requires careful definition, since there are always feedback effects in the climatesystem. One of the most important is water vapour; when greenhouse gas concentrationsrise and increase the quantity of solar radiation retained by the Earth system, thatwarming increases the amount of water vapour held in the atmosphere. Since water vapour is itself a greenhouse gas, that feedback causes further warming. Because of feedbacks of this kind, every time the climate system gets pushed a little bit, it runsaway a bit further before coming to a new equilibrium. When I refer to runawaychange, I am not referring to this ordinary situation. Rather, I am talking about when

change begins to beget ever-more change, like a screeching microphone too close to aspeaker.

Runaway climate change would be a cascading amplification of warming in which positive feedbacks build upon one another and the climate system is ultimately put into aradically different state. This can be understood by analogy. When human activities alter the climate, it is a bit like rocking a vending machine back and forth. You can tilt it acertain distance forward or back and, when released, it rocks back to its original verticalstate. Pushing it into a runaway circumstance is like tilting it so far that it begins fallingover under its own weight. In the climate system, this could be caused by things likemelting ice vanishing, meaning less solar radiation gets reflected into space. It could also

arise partly from powerful greenhouse gases trapped under the ground and sea in theArctic escaping because the air and water around them warm up.

In a worst-case scenario, this could make the entire planet permanently hostile to life. Weknow that planets can move from a state potentially hospitable to life to one that is utterlyhostile. At one point, there was liquid water on the surface of Venus. A brightening suncaused runaway climate change on that planet, and now the mean surface temperature isover 400C. It is not known with certainty whether runaway climate change is possibleon Earth, or could be induced by human activity.

I think I have generally used these terms with these meanings in past posts on this siteand a sibilant intake of breath . I shall certainly endeavour to use them consistently in thefuture.

Avoiding dangerous climate change is an ethical necessity and highly desirable practically, though the political will to achieve it is entirely lacking globally. Avoidingcatastrophic or runaway climate change is absolutely necessary if any of the other ambitions of humanity are to be achieved. If we fail to achieve that, future generationswill be correct in cursing us for our selfishness and lack of vision.
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* For instance, in terms of parts per million of carbon dioxide equivalent in theatmosphere, in terms of changes in radiative forcing measured in watts per square metre,or in terms of mean surface temperature change.

The work of climatologists has found evidence to suggest that only a limited number of factors are primarily responsible for most of the past episodes of climate change on theEarth. These factors include:

Variations in the Earth's orbital characteristics. Atmospheric carbon dioxide variations. Volcanic eruptions Variations in solar output.

.

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The greenhouse effect

A layer of greenhouse gases primarily water vapor, and including much smaller amounts of carbon dioxide, methane and nitrous oxide act as a thermal blanket for theEarth, absorbing heat and warming the surface to a life-supporting average of 59 degrees

Fahrenheit (15 degrees Celsius).

Most climate scientists agree the main cause of the current global warming trend ishuman expansion of the "greenhouse effect" 1 -- warming that results when theatmosphere traps heat radiating from Earth toward space.

Certain gases in the atmosphere block heat from escaping. Long-lived gases, remainingsemi-permanently in the atmosphere, which do not respond physically or chemically tochanges in temperature are described as "forcing" climate change whereas gases, such aswater, which respond physically or chemically to changes in temperature are seen as"feedbacks."

Gases that contribute to the greenhouse effect include:

Water vapor. The most abundant greenhouse gas, but importantly, it acts as afeedback to the climate. Water vapor increases as the Earth's atmosphere warms,

but so does the possibility of clouds and precipitation, making these some of themost important feedback mechanisms to the greenhouse effect.
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Carbon dioxide (CO 2). A minor but very important component of the atmosphere,carbon dioxide is released through natural processes such as respiration andvolcano eruptions and through human activities such as deforestation, land usechanges, and burning fossil fuels. Humans have increased atmospheric CO 2concentration by a third since the Industrial Revolution began. This is the most

important long-lived "forcing" of climate change. Methane. A hydrocarbon gas produced both through natural sources and human

activities, including the decomposition of wastes in landfills, agriculture, andespecially rice cultivation, as well as ruminant digestion and manure managementassociated with domestic livestock. On a molecule-for-molecule basis, methane isa far more active greenhouse gas than carbon dioxide, but also one which is muchless abundant in the atmosphere.

Nitrous oxide. A powerful greenhouse gas produced by soil cultivation practices,especially the use of commercial and organic fertilizers, fossil fuel combustion,

nitric acid production, and biomass burning. Chlorofluorocarbons (CFCs). Synthetic compounds of entirely of industrial origin

used in a number of applications, but now largely regulated in production andrelease to the atmosphere by international agreement for their ability to contributeto destruction of the ozone layer. They are also greenhouse gases .

Not enough greenhouse effect: The planet Mars has a very thin atmosphere, nearly allcarbon dioxide. Because of the low atmospheric pressure, and with little to no methane or water vapor to reinforce the weak greenhouse effect, Mars has a largely frozen surfacethat shows no evidence of life.


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In its recently released Fourth Assessment Report, the Intergovernmental Panel onClimate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 90

percent probability that human activities over the past 250 years have warmed our planet.

The industrial activities that our modern civilization depends upon have raisedatmospheric carbon dioxide levels from 280 parts per million to 379 parts per million inthe last 150 years. The panel also concluded there's a better than 90 percent probabilitythat human-produced greenhouse gases such as carbon dioxide, methane and nitrousoxide have caused much of the observed increase in Earth's temperatures over the past 50years.

They said the rate of increase in global warming due to these gases is very likely to beunprecedented within the past 10,000 years or more. The panel's full Summary for Policymakers report is online at http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf .

Solar irradiance

It's reasonable to assume that changes in the sun's energy output would cause the climateto change, since the sun is the fundamental source of energy that drives our climatesystem.

Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity is thought to have triggered the Little Ice Age

between approximately 1650 and 1850, when Greenland was largely cut off by ice from1410 to the 1720s and glaciers advanced in the Alps.

But several lines of evidence show that current global warming cannot be explained bychanges in energy from the sun:

Since 1750, the average amount of energy coming from the Sun either remainedconstant or increased slightly.

If the warming were caused by a more active sun, then scientists would expect tosee warmer temperatures in all layers of the atmosphere. Instead, they haveobserved a cooling in the upper atmosphere, and a warming at the surface and inthe lower parts of the atmosphere. That's because greenhouse gasses are trapping

heat in the lower atmosphere. Climate models that include solar irradiance changes cant reproduce the observed

temperature trend over the past century or more without including a rise ingreenhouse gases.
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mauritius: addressing climate changedamage to island livelihoods

Mauritius is among Africas top nations in terms of GDP and living standards. However,on Rodrigues, a semi-autonomous island district 560 kilometres north-east of MauritiusIsland, livelihoods and productivity have been deeply affected by climate change. Asfarmers and fishers ability to export their produce falls, poverty is on the rise.

The goal of this project was to build awareness and capacity about the impacts of climate change on the vulnerable groups of Rodrigues Island.

what happened: Friends of the Earth Mauritius / MAUDESCO carried out an island-wide survey of fisher and farming communities and their families. This includedconsultative meetings with these target groups, as well as additional meetings to trainthose who carried out the survey. Four seminars were also organized with the targetgroups, plus an additional national seminar and workshop to share the survey findings.The latter one-day seminar/workshop was bolstered by the attendance of Aldrin Calixteof Friends of the Earth Haiti.

The FoE Mauritius surveys confirmed that the island is heavily impacted by climatechange, farming and fishing in particular. Local people report less rainfall, with winters

becoming colder and summers becoming hotter. Soil fertility is decreasing, and livestock growth and food crop production have been negatively affected. There is a noticeable lossof biodiversity, while formerly eradicated insects and parasites have returned, allcombining to increase farmers poverty.

As for fishing, respondents report rougher seas which hamper fishing, cooler waters, andmore energy and money expended on smaller catches. They complained that the sea ismore polluted, and that the islands major lagoon is virtually without fish, while somefish species have disappeared from the seas. They also note that the sea level is rising.

The four capacity-building, awareness-raising seminars were very well attended byalmost 300 participants, while the national seminar was attended by over 150 peoplerepresenting the three impacted groups, the majority being women.

what is changing: The project was to cover mitigation activities to some extent. Thoughno funds were clearly earmarked for this, the seminars / workshops stressed theimportance of preserving the environment and preventing climate change through asustainable lifestyle. Activities put forward included tree planting, especially multi-

purpose tree varieties, and energy and water conservation. Aldrins presentation providedexamples of how these steps are taken in Haiti. The message we left was clear: by
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adopting very simple actions one can contribute directly to preserve the environment and prevent climate change it is all a question of individual attitudes, said Rajen Awotar of FoE Mauritius.

what we learned: Unlike on Mauritius, women play a frontline role in farming and

fishing in Rodrigues. Due to climate change impacts, they learned that most of their activities are now concentrated on feeding their families, with very little margin for excess production to sell to the markets.

The national seminar provided participants with the golden opportunity to learn aboutHaiti through Aldrin Calixte, a country with many similarities to the Republic of Mauritius. Attendees expressed the need for an exchange program to share experiences

between the two countries.

The national seminar made it clear that small-island states such as Rogdrigues, Mauritiusand Haiti are particularly vulnerable to climate change. It also become clear that these

effects have probably been felt for a fairly long period of time, but have only just recently been attributed to climate change.

Furthermore, they addressed the fact that these countries have no instruments, such ascrop insurance, to cushion these impacts. The only policy for assistance to impactedcommunities was a very weak financial scheme in Mauritius and Rodrigues for fisherswho face bad weather. Therefore they also discussed the Adaptation Fund set up in Bali,stressing the importance of representing the impacted groups in the Mauritius NationalAdaptation Fund likely to be set up under its provisions.

what next: It is evident that there is an urgent need to build the capacity, information,and awareness-raising levels of the impacted groups regarding project identification andformulation, to enable them access the Adaptation Fund. FoE Mauritius also stressed thefact that these groups should be part of the process and not outsiders, despite the distancefrom Mauritius.

with thanks to our funders: the sigrid raus in g trust
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defining climate change terms

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