GLOBAL WARMING

GLOBAL WARMING

Global climatic change due to increasing atmospheric concentrations

of so-called ‘greenhouse gases’ (notably carbon dioxide and chlorofluorocarbons

or CFCs) has dominated the environmental agenda

since the mid-1980s and has engendered considerable international

political debate. There is little doubt that over the past century human

action has significantly increased the atmospheric concentration of

several gases that are closely related to global temperature. These

increased concentrations, which are set to continue to rise in the near

future, are already affecting global climate, but our poor knowledge

and understanding of the workings of the global heat balance make the

present and future situation uncertain.

Global warming is closely connected with the impact of rises in

greenhouse gases on the thin layer of ozone present in the stratosphere

above the earth. Ozone absorbs incoming ultraviolet radiation from

the sun, thus preventing the earth from overheating. In 1985 scientists

discovered what soon became identified as a hole in the ozone layer

over the Antarctic. Today, the hole is no longer confined to the Southern

Hemisphere, since stratospheric ozone depletion has now been

identified in the Northern Hemisphere and in the Arctic. Despite

prompt international action to reduce chlorofluorocarbons, past emissions

will continue to cause ozone depletion for decades to come

because of the time lag between their production and release into the

atmosphere and their damaging effects. Full recovery is not expected

until about 2050 at the earliest. Meanwhile the increase in ultraviolet

radiation reaching the earth’s surface is compounded by the fact that

greenhouse gases are transparent to incoming short-wave solar radiation

even though they absorb re-radiated long-wave radiation from

the earth’s surface. Hence the term ‘greenhouse’.

The theory relating increased atmospheric concentrations of

greenhouse gases and global warming is strongly supported by evidence

showing that changes in the atmospheric concentrations of

greenhouse gases have fluctuated in close harmony with global temperature

changes, indicating that the two are related. There is alsoevidence to suggest that the twentieth century is the warmest of the

second millennium. Overall, the planet has warmed at the surface by

about 0.6C over the past century. In part, this reflects the operation of

an enhanced greenhouse effect due to human pollution of the

atmosphere.

It is important to note that the warming trend over the past century

has not been continuous through either time or space. Two periods of

relatively rapid warming (from the 1910s to the 1940s and again from

the mid-1970s to the present) contrast with preceding periods which

were respectively characterised by fairly unchanging (1860s to 1900s)

and slightly declining (1940s to 1970s) temperature. Spatially, too,

global warming has been discontinuous: the two hemispheres have not

warmed and cooled in unison; moreover highly industrialised areas

appear to be warming at a slower rate than less industrialised regions.

The formidable economic, social, and political challenges posed to

the world’s governments and other policymakers by impending global

climatic change are unprecedented. Policy responses can be categorised

broadly into those that aim to prevent change, and those that

accept the changes and focus upon adapting to them. While the issue is

a truly global one, since all greenhouse gas emissions affect climate

regardless of their origin, the costs and benefits of measures to mitigate

the effects of global warming are likely to spread unevenly across countries.

The issue raises important questions of international equity since,

at present, the major proportion of greenhouse gas emissions comes

from the industrialised countries, which contain only about one quarter

of the world’s population. Third World states have called for

reductions in emissions from the industrialised countries to make more

of the planet’s capacity for assimilation of greenhouse gases available to

those countries that are industrialising now, a plan which should be

facilitated by transfers of finance and technology from the North to the

South.

Most countries have accepted the need to make some effort to

prevent global warming, or at least to slow its pace, by reducing greenhouse

gas emissions. A contribution has been made in this respect by

the Montreal Protocol, which was signed in 1987 and amended in

1990. Governments have committed themselves to reduce consumption

and production of substances that deplete the stratospheric ozone

layer, many of which also contribute directly to global warming. CFCs

were due to be phased out by the year 2000. Most attention since then

has been focused on carbon dioxide. In 1992, more than 150 states

participated in the United Nations Framework Convention on

Climate Change (the Earth Summit). They agreed to reduce emissionsto earlier levels, in many cases the voluntary goal being a reduction of

carbon dioxide emissions to 1990 levels.

An attempt to make agreed reductions legally binding was made in

1997 at the Kyoto Protocol, a follow-on to the original climate treaty,

although the United States has now withdrawn from the Kyoto

agreement. Kyoto also focused on a wider range of greenhouse gas

emissions such as methane and nitrous oxide. The declared aim of the

Protocol is to cut the combined emissions of greenhouse gases by

about 5 per cent from their 1990 levels by 2008–12, specifying the

amount each industrialised country must contribute towards this overall

aim. Those countries with the highest carbon dioxide emissions,

including the United States, Japan, the European Union, and most

other European states, are expected to reduce their emissions by 6 to 8

per cent. In practice, individual country reductions can be greater or

less than those agreed, since the Kyoto Protocol also officially sanctioned

the idea of emissions trading between industrialised countries.

Hence, if a state’s emissions fall below its treaty limit, it can sell credit

for its remaining allotment to another country to help the buyer meet

its treaty obligation.

Realistically, however, no government is likely to sacrifice significant

economic growth for reductions in carbon dioxide emissions, so

that long-term strategies to reduce emissions must uncouple economic

growth from increasing fossil fuel consumption. Reducing the amount

of energy used per unit of gross domestic product (GDP) will be one

element in such a strategy, but there is also a need for a significant shift

away from fossil fuels to more renewable energy resources. Many

industrialised countries do have experience of economic growth with

declines in energy consumption. It occurred during the late 1970s and

early 1980s, sparked by the 1970s oil crisis. Unfortunately, virtually all

governments have reinstated their faith in the belief that economic

growth must be based on an increase in energy consumption. But

the lessons of global warming make it clear that this kind of industrialisation,

based on an inefficient use of fossil fuel resources, is not a

sustainable form of development.