Climate Change: What Every Citizen Should Know
Weekend Essay, Australian Financial Review, September 27, 2003
PUBLIC debate regarding climate change is charged with great emotion, not least because so much of the comment is driven by pressure groups with strong political agendas.
There are many science facts to do with climate change, and innumerable theories which claim to explain these facts, but the essence of the matter can be communicated in six questions and their brief answers.
Here they are.
Q1. Is climate change occurring?
A. Yes, of course. Climate change is always
Throughout Earth’s history, both geographic and climate change have been continuous. For instance, 450 million years ago the rocks which now form the top of Mt Everest were sedimentary deposits in an ancient ocean, at a time when global atmospheric carbon dioxide levels, and temperatures, were from time to time appreciably higher than today.
Dramatic climate change has been particularly characteristic of the most recent 2,500,000 years of earth history. Over this period, the Earth has experienced about 100 alternately glacial and interglacial episodes. This climatic cycling occurred especially on periodicities of about 20,000, 40,000 and 100,000 years, as manifest by glaciers waxing and waning, the ocean level rising and falling, and the global average temperature varying by 60 C or more.
The wonderful planetary biodiversity, which all of us so enjoy and wish to protect, results in no little part from the vicissitudes of climate change which have shaped Earth’s modern ecosystems. These vicissitudes continue.
Q2. Is the global climate currently getting
A. Without being precious, it depends upon what you mean by (i) "global climate" and (ii) "currently".
To the degree that a single number (average
temperature) can usefully be said to characterise the Earth’s climate, the
climate was cooling during the 1970s, and is warming now, but in neither case at
exceptional rates. The strongest evidence for warming occurs in climate records
from Northern Hemisphere middle and higher latitudes, i.e. in records which are
The answer to this question also depends upon how you agree to measure global temperature. For instance, averaged temperature measurements made with thermometers from all over the world indeed suggest that an overall rise of almost 10 C occurred during the 20th century. However, alternative and highly accurate measurements of atmospheric temperature are available since 1958 from weather balloons, and 1979 from satellites. These temperature records agree with each other within the measurement error, and neither shows any overall warming over the last 45 years.
Many, but not all, scientists believe that the averaged thermometer measurements disagree with the satellite and weather balloon measurements because they have not been corrected sufficiently for the “heat island” effect. This effect, for which thermometer measurements are corrected already, results from the fact that many thermometers are located near manmade connurbations or structures, where, because these features absorb and then re-radiate incoming solar heat, they record an increase in local temperature.
Q3. If the climate is getting warmer now, is it an human-caused effect?
A. Basic physics tells us that increasing greenhouse gases (such as carbon dioxide) in the atmosphere, some part of which is human-caused, will have a warming effect.
Alarmist computer models notwithstanding, any such effect has not yet occurred at a measurable level which can be distinguished from natural variation. More specifically, the pattern of "global" temperature change over the last 100 years does not match the smoothly-increasing curve of atmospheric carbon dioxide which is so widely alleged to be the cause.
Additionally, the ancient climate record shows that
in the past increasing temperatures preceded increases in carbon
dioxide. This means that in the real world, as opposed to the idealised computer
world, atmospheric carbon dioxide content cannot be the primary cause of global
warming. In this regard, it should always be remembered too that the computer
models which predict 1-60 C of future warming from greenhouse gas
accumulation are no more and probably no less reliable than computer models
which predict the future of the stock market.
Q4. Is present-day climate change occurring at rates, or does it reach extremes, which lie outside the natural behaviour of climate in the past?
A. Absolutely not.
The Intergovernmental Panel on Climate Change’s (and many scientists’) fixation with judging modern trends against the last 1000 years is intellectually lazy, if not actually dishonest. There is nothing whatever about the last 1000 years of Earth history that has any especial relevance to judging contemporary climate change.
If you wish to choose a more scientifically justifiable period of time, then it would either be: (i) the last 10,000 years (during which climate has been as much as 20 C warmer or cooler than today), (ii) the last 20,000 years (during which we have gone from an ice age to an interglacial; i.e. a shift in global average temperature of 6-80 C), (iii) the last 125,000 years (which is when the last warm interglacial period occurred, which was about 40 C warmer than today), or (iv) the last 340,000 years (when, during warm period interglacial 9, temperature may have been as much as 60 C warmer than today).
When the ancient climatic record is examined on these timescales it is seen to encompass many occasions of rapid climate change. During such an episode the temperature at a particular site can swing from almost full glacial to full interglacial conditions, or the other way round, in periods as short as one or two decades. The mechanism controlling these rapid swings remains unknown, and for all we know one could have started yesterday. Reassuringly, perhaps, in the past rapid climate changes seem to have been commoner during glacial periods compared to interglacials such as the one we live in today.
Q5. But we hear so many scientists claiming that global warming is a problem. Surely, where there is so much smoke there must be fire?
A. The proverb that “where there’s smoke there’s fire”, like most proverbs, is as often untrue as it is true. In the case of global warming, however, the truism turns out to be true.
The fire is fuelled by the many billions of $US which are now spent worldwide each year on climate change research, and the smoke comes from the opinions of the more than 100,000 scientists who are employed to investigate the problem. Don’t get angry with them, but rather extend your sympathy: after all, without there being an acute climate change problem there will be many fewer science jobs.
Q6. Will adhering to the Kyoto Protocol cause a significant reduction in global warming?
A typical computer model projection predicts that implementing the Kyoto Protocol would reduce an expected temperature increase of 2.10 C by 2100 to 1.90 C instead. Put another way, the world would postpone until 2100 a temperature increase which would otherwise occur in 2094. About a trillion dollars, which is the estimated cost of the Kyoto accord, seems a lot of money to spend to buy just six years of breathing space. As Bjorn Lomborg never tires of pointing out, a better use of this money would be to spend it alleviating some of the much more acute global problems, such as starvation, sanitation and health services in less privileged countries.
Essex, C. & McKitrick, R. 2002 "Taken by Storm. The Troubled Science, Policy & Politics of Global Warming", Key Porter Books, Toronto, 320 pp. (available from http://www.amazon.ca/exec/obidos/ASIN/1552632121/qid%3D1068703311/701-8325568-0601122)
Gerhard, L.E., Harrison, W.E. & Hanson, B.M. 2001 "Geological Perspectives on Climate Change". American Association of Petroleum Geologists, Studies in Geology, 47 (available from http://bookstore.aapg.org/detail.html?cat_no=527&ticket=0295038951468218&uniqueid=200311130111).
Gray, V. 2002 The Greenhouse Delusion. A critique of "Climate Change 2001". Multi-Science Publishing Co. Ltd., Brentwood, Essex,
95 pp. (email@example.com) (available from http://www.multi-science.co.uk/index_books.htm).