Sunday, August 24, 2008

Case of the warm and fuzzy

Three claims have been repeated so often they are accepted as fact:  global temperatures are rising, we have less rainfall and so water is becoming scarce, and salinity in the Murray River is rising.

Of course there is the old adage:  lies, damn lies, and then there are statistics.  But we can keep it simple and just consider data from observations of the real world and from the most reputable institution since records began for the particular issue in which we are interested.  It is important to not confuse real-world data (also known as observational data) with output from computer models because computer models generate scenarios that may or may not come true.

Observational data on rainfall for the entire east coast of Australia is available from the Australian Bureau of Meteorology with yearly averages for all the sites back to 1900.

But, contrary to the Stern report, this chart does not show declining rainfall; rather, it indicates that rainfall was very low in the early 1900s, that there were some very wet years in the late '50s and early '70s, and overall the trend is one of a slight increase in rainfall during the past 107 years.

Stern got it wrong, perhaps because he was confusing output from computer models with the real-world data.  There are a lot of computer models that foretell dire environmental catastrophe that may not eventuate.

Rainfall data for the Murray-Darling Basin is also available from the Bureau of Meteorology.  The overall trend is one of increasing rainfall since 1900.  The past few years show below-average rainfall for the region and indeed there has been drought.  The low river inflows have been exacerbated by more groundwater pumping, more plantation forestry, including in the upper Murrumbidgee, and more salt interception schemes along the Murray River.

Salt interception schemes evaporate water to trap the salt.  In the '80s, computer models predicted that Adelaide's drinking water soon would be too salty to drink because of declining water quality and rising salinity levels in the Murray River.  Measurements of salinity are recorded from many different sites along the Murray River, including at Morgan, which is immediately upstream from the offshoots from Adelaide's drinking water.  The data from Morgan enables us to get an idea of how salt levels are trending in the real world, as opposed to computer-generated scenarios.

Concerns with salinity have resulted in levels being tested from the '30s.  Salinity levels rose dramatically during the '70s and peaked at Morgan in 1982, which was a drought year.  Then the Murray-Darling Basin Commission implemented a catchment-wide drainage management plan and started building salt interception schemes, and since then salinity levels have more than halved.

Measuring global temperatures is much more contentious than measuring salinity or rainfall.  Issues include how to combine the data from all the weather stations across the globe and the data is usually presented as a temperature anomaly rather than, for example, just a global average.  A temperature anomaly is derived from the average temperature for a specific but arbitrarily defined period and usually emphasises the extent to which temperatures have increased.  The Bureau of Meteorology relies on the Climatic Research Unit at the University of East Anglia in conjunction with the Hadley Centre of the British Met Office for its information on global temperatures.  This information is available on the internet going back as far as 1850 and shows the deviation from the period 1961 to 1990.

But when global temperatures are presented just as a simple average with a vertical axis that spans the range of temperatures experienced in a place such as Ipswich (west of Brisbane) during a single year, the global rise in average temperatures is not that obvious because the mean temperature since 1850 has increased by less than 1°C.

The data from the CRU is generally accepted as accurate by those who subscribe to the idea that carbon dioxide is driving dangerous man-made global warming.  In contrast, many sceptics of man-made global warming argue that the only reliable measure of global temperatures is from satellites.

Ross McKitrick from Canada's University of Guelph argues that 50 per cent of global warming measured by land-based thermometers in the US since 1980 is due to local influences of man-made structures, also known as the urban heat island effect.  There also have been issues with the additions and losses of weather stations; for example, many weather stations were lost in places such as Siberia with the disintegration of the Soviet Union.

Thermometer temperature data has been collected in the polar regions only since the '40s and calculating the mean temperature at the poles is still difficult.

James Hansen, from the Goddard Institute for Space Studies, has explained the general difficulty of measuring surface temperatures.

"Even at the same location, the temperature near the ground may be very different from the temperature 5 feet (1.52m) above the ground and different again from 10 feet or 50 feet above the ground," he says.  "Particularly in the presence of vegetation (say in a rainforest), the temperature above the vegetation may be very different from the temperature below the top of the vegetation.

"A reasonable suggestion might be to use the average temperature of the first 50 feet of air either above ground or above the top of the vegetation.  To measure SAT (surface air temperature) we have to agree on what it is and, as far as I know, no such standard has been suggested or generally adopted."

Given these difficulties, an alternative is to use temperature data from satellites.  Since 1979, orbiting satellites have measured temperature in a completely different way from the traditional method of using thermometers.

The satellites measure microwave radiation and the research focus has been on getting a broadly representative measure of lower atmosphere temperature.

The satellite data is available only since 1979, but it does give a good overview of how global temperatures have been trending during the past 30 years.  Global temperatures peaked in 1998, associated with an El Nino warming event, then dropped quite dramatically before stabilising for a few years and dropping again recently.  The satellite data on global temperatures indicates we presently have a global cooling, not a global warming, trend.

Many scientists, environmental activists and politicians have staked their reputations on the idea that global temperatures are going to keep steadily rising, so it is not surprising that they are ignoring the past few years of data from the satellites.  But the stakes are very high.

The Australian Government is planning to introduce an emissions trading scheme, also described as a carbon pollution reduction scheme, on the basis that that carbon dioxide from the burning of fossil fuels is contributing to dangerous global warming.

Many people assume that such a drastic action is premised on good evidence establishing a proven causal link between anthropogenic carbon dioxide and global warming.

But it is not, instead relying on computer models, claims of a scientific consensus and the belief that global temperatures continue to creep higher and higher.  Many false claims are made about the state of our environment on an almost daily basis but, because most Australians are illiterate when it comes to science and maths, they are mostly just accepted.

Most Australians rely on television and newspapers for information about environmental issues.  If this reporting incorporated some charts, in the same way business reporting does as a matter of course, then there might be at least some quality control.

But, ultimately, good policy is going to require that a much larger percentage of Australians having a higher level of scientific literacy.

The alternative is important policy continuing to be decided on hearsay rather than evidence because you just can't trust the environmental advocates.  Indeed, they may care more about the environment than the truth.

MANY people want to save the environment, but few people are confident of interpreting a chart or graph of scientific information on, say, water quality or global temperatures.  So, when it comes to environmental issues most Australians just believe what the experts say.  After all, people who care about the environment are the good guys, caring and trustworthy.

Furthermore, when it comes to issues such as global warming, we are told there is a consensus, that most scientists agree about most things and this should make us feel even more secure believing what they tell us about the sorry state of planet Earth.  But who should check what the experts are saying about environmental issues, and at what point?  When it comes to business issues, whether interest rates or commodity prices, we are shown charts, hard data, and people who are interested in the business issues would expect no less.

Environmental issues are very much like business issues:  they are about numbers and trends.  For example, business analysts are interested in whether the price of oil is going up or coming down and Al Gore tells us that global temperatures are going up.  But if your next stock investment depended on what Gore was telling you the business market was doing, wouldn't you also seek information from other sources to be sure?

graphs


ADVERTISEMENT

No comments: