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Evidence For And Against Climate Change Environmental Sciences Essay

Paper Type: Free Essay Subject: Environmental Sciences
Wordcount: 1910 words Published: 1st Jan 2015

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Climate Change is a very controversial global issue which has committed supporters and detractors. Critically evaluate the evidence for and against climate change and provide your own assessment of the current and future risks that the planet faces by 2050.

It is expected that you will give a broad view of your subject giving weight to policy, regulatory, economic and risk management impacts as well as health and environmental impacts. Use a case study to illustrate a key component of the climate change agenda.

The world’s climate is changing and the consequences are serious, wide ranging and long-term. Despite the overwhelming scientific consensus that this is happening, the issue of climate change has it’s detractors, whose opposition to the phenomenon range from disagreeing about the extent of the problem, the extent of man’s influence, to the accuracy of the modeling techniques. During the essay the evidence from both sides will be evaluated and the current and longer term economic, social, and environmental effects assessed.

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The definitions of climate change vary greatly, but the two most useful are the United Nations Framework Convention on Climate Change (UNFCCC) definition where broadly speaking climate change relates to a change in climate which is attributed, directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods and the Intergovernmental Panel on Climate Change (IPCC) which refers to any change in climate over time, whether due to natural variability or as a result of human activity, which is perhaps a more useful definition.

Firstly before looking at the evidence for climate change it is useful to understand the global energy flow (radiative budget), which was first suggested by Kiehl and Trenbirth (1997), illustrated in picture 1 below:

Picture 1

The incoming solar radiation, often labelled in percentage terms, must match the outgoing short and longwave radiation to achieve “radiative equilibrium”. Radiative forcing is the measure of the influence that a specific factor has in altering the balance of this incoming and outgoing energy, and is therefore a useful indication of the importance of that factor to change the climate. Positive forcing will generally mean that the surface of the earth is warmed, whilst negative forcing tends to cool the surface.

The Kyoto protocol, adopted in December 1997 and entering into force in February 2005, committed all Annex1 countries (39 industrialised countries & the EU) to a reduction in four greenhouse gases (Carbon dioxide, Methane, Nitrous oxide and Sulfur hexafluoride) and two groups of gases called hydrofluorocarbons (HFCs) (often found in refridgerants) and perfluorocarbons (PFCs) (also in refridgerants but having a wide variety of medical and non-medical uses and according to Askam, Khalil et al. (2003) having a lifetime up to 50,000 years).

Carbon dioxide is perhaps the most studied and well known of the anthropogenic GHGs. Since some infra-red radiation leaving the planet is absorbed by CO2, the greater the CO2 the greater the absorbtion and reflection of heat and the warmer the climate.

Perhaps the most significant indicator of the increase in the level of CO2 in the last 50 years is shown in graph 1 below. This is the measurement of CO2 concentrations as measured in Hawaii, far from industrial areas so no localised bias is present, though these measurements have been replicated around the world (e.g. Pieter P. Tans and Thomas J. Conway 1968-2002) Monthly Atmospheric CO2 Mixing Ratios from the NOAA Climate Monitoring and Diagnostics Laboratory Carbon Cycle Cooperative Global Air Sampling Network, 1968-2002. NOAA Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80305, U.S.A.)

Graph 1

Image created by Robert A. Rohde / www.globalwarmingart.com

Similar measurements have been found in ice core samples, which enable us to get a much better picture over time. Graph 2 below shows the CO2 variations over time from the past 420,000 years.

Graph 2

Image created by Robert A. Rohde / www.globalwarmingart.com

This shows the CO2 levels fluctuating in line with the ice-ages, however, the most important section is the insert – the marked increase since the industrial revolution from around 1750/1800. A clear indication of human’s influence.

More evidence is given in the IPCC 4th Annual Report Working Group summary that the concentration of atmospheric CO2 has increased from 280ppm (pre-industrial level) to 379ppm in 2005. In addition the annual CO2 concentration growth was larger during the last 10 years (1995-2005 : 1.9ppm per year) than it has been since the beginning of continuous direct atmospheric measurements (1960-2005 : 1.4 ppm per year).

In a similar fashion the levels of Methane (from a pre-industrial level of 715ppb to 1732ppb in the early 1990s and 1774ppb in 2005) and Nitrous oxide (from pre-industrial levels of roughly 270ppb to 319ppb in 2005) have increased markedly over recent years.

Looking at the radiative forcing discussed earlier the

There are many different indications of how the climate has altered, and over several different timescales – ranging from the most recent 150 years since 1860, since roughly the time of industrial revolution since 1750 and for the past 10-100 thousand years. Each of these will be looked at in turn.

The Inter-governmental Panel on Climate Change in its most recent report in 2007 stated:

‘Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.’

‘Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns’

The time series shows the combined global land and marine surface temperature record from 1850 to 2009. The year 2009 was the sixth warmest on record, exceeded by 1998, 2005, 2003, 2002, and 2004. This time series is being compiled jointly by the Climatic Research Unit and the UK Met. Office Hadley Centre. The record is being continually up-dated and improved (see Brohan et al., 2006). This paper includes a new and more thorough assessment of errors, recognizing that these differ on annual and decadal timescales. Increased concentrations of greenhouse gases in the atmosphere due to human activities are most likely the underlying cause of warming in the 20th century.

Brohan, P., J.J. Kennedy, I. Harris, S.F.B. Tett and P.D. Jones, 2006: Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850. J. Geophysical Research 111, D12106, doi:10.1029/2005JD006548



In a debate that has become highly polarised the label ‘climate sceptic’ is readily slapped on anybody who stands on the soapbox and contradicts Al Gore. In reality, the sceptic landscape is more varied, ranging from those scurrilously pursuing scientific truth to others with more obvious economic or political gains to play for.

Richard Lindzen, an American atmospheric physicist at the Massachusetts Institute of Technology has been one of the most vocal in expressing concerns over the validity of computer models used to predict future climate change. He argues that they may be over-predicting future warming due to a failure to properly account for the climate system’s water vapour feedback. However he has also been an active contributor to Intergovernmental Panel on Climate Change assessment reports.

Gavin Schmidt, a climatologist at the NASA Goddard Institute for Space Studies commented that Lindzen agrees with about 90 per cent of what other climate scientists are saying, yet the last 10 per cent is sufficiently different to label him a contrarian.

Stephen McIntyre, editor of “sceptic” blog ClimateAudit and former director of several state-owned Canadian mineral exploration companies, is known in the climate science community for his continual demands for raw data.

McIntryre was behind an orchestrated campaign that led to 60 Freedom of Information requests being made to CRU scientists at the University of East Anglia in a single weekend in July.

However, while potentially vexatious, McIntyre has made genuine scientific contributions, notably spotting a mistake in NASA data that led to the average US temperatures to be reduced about 0.15C for the period 2000-2006.

Philip Stott, an emeritus professor of biogeography at the University of London (although not a published climate scientist), has publicly argued that the climate is too complex and chaotic a system to make long-term predictions on.

None of these scientists are climate change deniers, but they question the certainty of the scientific consensus.

Several Tory MPs have recently contradicted the Green Conservative line of the Cameron era.

Peter Lilley, one of only three MPs to vote against the government’s Climate Change Bill in October, has accused climatologists of an “unconscious conspiracy” in which a dogmatic determination to conform to a consensus driven by the incentive of public funding has made them happier to let the data fit the theory rather than the opposite.

David Davis has also spoken out on what he describes as a “ferocious determination to impose hair-shirt policies on the public”. Taxes on holiday flights and noisy wind turbines are too high a price to pay, he suggests. Both MPs claim to be open to the possibility that man has significantly contributing to climate change, but both remain unconvinced by the evidence.

Former Tory Chancellor Nigel Lawson, has also publicly stepped up his opposition to environmental policy, founding the think tank, the Global Warming Policy Foundation, complete with a board of fairly distinguished academics to provide scepticism with a “respectable face”. However, the think tank was this week accused by scientists of appearing to misrepresent scientific data on its website.

At the far end of the spectrum, figures such as Sarah Palin appear to be happy to disregard scientific evidence wholesale in favour of economic gain.

Despite substantial differences in outlook, bundled together under the “sceptic” brand, the views of these individuals appear to be increasingly gaining favour with the public in the lead up to Copenhagen.


For climate change

Against climate change

Case study

Assessment of current risks

Assessment of future risks to 2050


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