Debunking the myths of the climate sceptics

Climate myths: some examples

By "climate myth", I mean opinions on climate science which contradict those of mainstream climate textbooks and the assessment reports of the Intergovernmental Panel on Climate Change (IPCC). They are generally put forward by lobby groups with close links to fossil fuel and related industries and the handful of scientists who agree with them.

Some "myths" are simply the result of quoting incorrect data, but most are more sophisticated, distorting the available evidence. (The notes (a), (b) etc refer to some examples of climate sceptic documents.)

1. Current climate change is little more than natural variation [a, b]

• some sceptics argue that climate has always varied, eg, the ice ages, and hence current climate change is (mostly or wholly) just the latest natural variation

• sceptics accept human activities emit billions of tonnes of CO₂ and other greenhouse gases into the atmosphere (to deny this would be denying basic chemistry)

• sceptics also accept that atmospheric levels of these gases have risen significantly over industrial period due to these emissions (data from eg atmospheric measurements, bubbles of gas trapped in ancient layers of ice)

• what sceptics argue is that warming effect due to these higher atmospheric GHG levels is negligible

• this downplays the direct heat-trapping properties of GHGs and ignores the indirect feedback effects which enhance the warming, the most important being that the levels of the longer-lived GHGs, eg CO₂, determine the atmospheric levels of water vapour, a very powerful but short-lived GHG

• estimates of the total warming effects of GHGs can only be produced using mathematical models which include these feedback effects. Models are based on a combination of experimental physics and observations of GHG levels, temperature and many other conditions

• a wide range of maths models show that the recent temperature changes are mainly explained by the higher atmospheric levels of GHGs caused by humans. Natural effects such as solar variations or volcanic eruptions are inadequate

Climate science refs: [1]

2. Current climate change is caused by the Sun

• the Sun is obviously very important factor in Earth's climate, eg variations in solar energy reaching the Earth are a major factor in moving in and out of ice ages (due to long-term changes in the Earth's orbit around the Sun)

• some sceptics argue that historic variations in global temperature correlate well with changes in incoming solar energy and that this solar energy is now at a level higher than for several centuries

• however, these recent variations are so small that they do not adequately explain the size of the current temperature changes

Climate science refs: [2]

3. CO₂ is a minor/irrelevant gas - most of the warming is due to water vapour [a, b]

• see (1) above

• atmospheric level of water vapour varies considerably over time and space. The main factor which determines its level is that of long-lived GHGs such as CO₂

Climate science ref: [3]

4. Most glaciers are not shrinking [c]

• some sceptics have claimed most glaciers are advancing, eg Bellamy claimed 555 of 625 main glaciers have been growing since 1980

• however, the vast majority of glaciers are actually retreating, eg 79 out of 88 surveyed in 2002/03 by the World Glacier Monitoring Service - the small number not retreating is as a result of more complex local climate conditions

• a significant proportion of glaciers began retreating before human emissions of GHGs began to have an impact, eg many in Africa, because of natural climate variation. However, natural variation does not explain the continued and accelerated retreat that has been seen in recent decades, only human-produced global warming does

Climate science ref: [4]

5. Raised CO₂ levels are good for the Earth as they increase plant growth [a, b]

• some sceptics claim that higher levels of CO₂ in the atmosphere are positive as they accelerate plant growth

• some increase in CO₂ levels does indeed increase plant growth - this is known as the CO₂ fertilisation effect (NB different plants benefit by different degrees, eg 'C3' plants (eg soya) benefit much more than 'C4' plants (eg maize), which can change ecosystems)

• however, for larger rises in CO₂, the resulting temperature increase stresses plants causing them to die back

• both this effect and the increase in respiration from soil microbes, which also occurs at higher temperatures, leads to further emissions of CO₂ accelerating the warming

Climate science ref: [5]

6. Satellite data shows the Earth's temperature is fairly constant

• temperature data from satellites (and balloons) does show a smaller increase than ground-based observations, but it is not zero

• most importantly, the temperature recorded by these measuring devices is at a higher altitude and a lower warming is expected at this level (indeed, at even higher altitudes global warming leads to cooling of that part of the atmosphere as more heat is trapped at the surface)

Climate science ref: [6]

By contrast, some examples of real debate among climate scientists [7]

1. Clouds

• different types of clouds affect the climate in different ways. Low cloud tends to reflect solar radiation back into space while high cloud tends to trap more heat

• best estimates indicate that changes in cloud cover will significantly enhance the effect of human GHG emissions

• but significant uncertainty remains

2. Climate sensitivity

• climate sensitivity is the global temp change for a doubling in atmospheric CO₂ level

• the IPCC's best estimate is 2.5°C, but generally acknowledges that it could be between 1.5°C and 4.5°C (the main source of uncertainty being the changes in cloud cover)

• however, a recent paper in Nature, the climateprediction.net experiment, carried out the most extensive uncertainty analysis of climate models so far and concluded by that climate sensitivity could lie between 2°C and 11°C

3. "Hockey stick" graph

• this is the graph of global temp change over the last 1000 years which shows 900 years of relative temperature stability followed by a marked rise over the last century

• while there is little dispute about the data over the most recent 400 years, the measurements earlier than that (based on different data sets) are more uncertain

• for example, more localised data sources point to a more marked warm period in Medieval times and a more marked cool period (the "little ice age") around the 1700s

• however, the recent warming trend and its link to human emissions is unaffected by this

There are many more such areas of debate.

IPCC: background

• Intergovernmental Panel on Climate Change is scientific body set up in 1988 by the UN Environment Programme and the World Meteorological Organisation

• its remit is "to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation"

• its main activity is to compile three "assessment reports" roughly every 5 years summarising the latest underlying science, impacts and policy options

• IPCC composed of scientists from relevant fields and meets in plenary sessions to:

  • elect Chair and Bureau which oversee the work

  • approve reports

• input to last assessment report in 2001 involved about 3000 scientists

Climate sceptic organisations

A few examples:

• Scientific Alliance - UK group set up in 2001 to counter views of environmental movement; co-founder was Director of British Aggregates Association; has links to industry and right-wing groups

• Institute of Economic Affairs (IEA) - UK free-market and anti-environmentalist think-tank set up in 1950s

• American Enterprise Institute - oldest US neo-conservative think-tank with very close connections to Bush administration and major US corporations

• Junkscience.com - US website with extensive climate sceptic pages

• European Science and Environment Forum (ESEF) - possibly now defunct, this was co-founded by a senior member of the IEA

The NGO, Lobbywatch, has documented the political and industrial links of many of the main climate sceptic groups (and many others!) - see http://www.lobbywatch.org/

Interestingly, David Bellamy has very few if any connections with industry lobby groups. It seems his criticisms were at least partly motivated by his opposition to wind farms. However, he did decide to "bow out" of the climate science debate last year when George Monbiot demonstrated how dodgy the sources of his information were (Monbiot, 2005).

References

Climate science:

[1] Chapters 2-5 of Houghton (2004). See also IPCC (2001).

[2] Chapter 4 of Houghton (2004). See also IPCC (2001).

[3] p90-91 of Houghton (2004). See also [1].

[4] Pearce F. (2005). The flaw in the thaw. New Scientist, 27 August, p27-30. See also: World Glacier Monitoring Service website at: http://www.wgms.ch/

[5] p40 & 166 of Houghton (2004)

[6] p58-59 of Houghton (2004)

[7] Chapters 4, 5, 6 & 9 of Houghton (2004) & Stainforth D. et al (2005).

Houghton J. (2004). Global Warming: the complete briefing (3^rd ed). Cambridge University Press. http://www.cambridge.org/

IPCC (2001). Climate Change 2001: the scientific basis. Working Group I of the Intergovernmental Panel on Climate Change. Cambridge University Press. http://www.ipcc.ch/

Stainforth D. et al (2005). Uncertainty in predictions of the climate response to rising levels of greenhouse gases conditions. Nature, Vol 433, p403-406. http://www.nature.com/

Climate sceptics articles:

[a] Bellamy D. (2004). Global Warming? What a load of poppycock! Daily Mail, July 9.

[b] Junkscience (2006). The Real "Inconvenient Truth". Greenhouse, global warming - and some facts. http://www.junkscience.com/Greenhouse/

[c] Bellamy D. (2005). Letter in: New Scientist, 16 April.

Also:

Lobbywatch; http://www.lobbywatch.org/

Monbiot G. (2005). Junk science. 10 May. http://www.monbiot.com/archives/2005/05/10/junk-science