Global Warming Science Moves On
Dr David Evans
On global warming, public policy is where the science was
in 1998. Due to new evidence, science has since moved off in
a different direction.
The UN science body on this matter, the IPCC, is a political
body composed mainly of bureaucrats. So far it has resisted acknowledging
the new evidence. But as Lord Keynes famously asked, "When
the facts change, I change my mind. What do you do, sir?"
Four things have changed since 1998.
First, the new ice cores shows that in the six global warmings
over the past half a million years, temperature rises and falls
occurred on average 800 years before the accompanying
rises and falls in atmospheric carbon. The carbon rises could
not have either started or ended the temperature rises. So there
must be natural influences on global temperatures that are more
powerful than atmospheric carbon levels.
This 800 year lag became known and past dispute by 2003, which
is significant. The old ice core data, collected from 1985 to
1998, was low resolution: the data points were more than a thousand
years apart. It showed carbon and temperature moving in lockstep,
and it was the only supporting evidence we ever had for the notion
that carbon caused temperature. It seemed too good to be true-it
appeared we could control the temperature of the plant just by
adjusting the levels of a minor gas!
Watch Al Gore's movie carefully. The old ice core data is
the only evidence he presents for believing that carbon emissions
cause global warming. But by 2003 we had found the 800 year lag,
so then we knew that temperature caused carbon, not the other
way around as previously assumed. Al Gore's movie was made in
2005 so it was misleading of him not to mention the new ice core
data. Would anyone have believed his pitch if he had mentioned
that the alleged cause (rising and falling carbon levels) happened
800 years after the effect (rising and falling temperatures)?
Secondly, with the reversal of the ice core evidence, there
is now no evidence that carbon emissions cause significant global
Evidence is a set of observations by people of events. The
scientific method demands evidence-theory, politics, and vested
interests are all trumped by evidence. The scientific method
evolved as our best method for obtaining reliable information,
precisely because it was immune from forces such as power and
It is important to realize what is not evidence that
carbon emissions cause global warming. There is ample evidence
that global warming has occurred, but it says nothing about the
causes of that warming. Serious theoretical calculations for
the amount of warming by 2100 range from an inconsequential 0.24°C
to a catastrophic 6.2°C, but theory (including computer models)
is not evidence. Comparison of model outputs to observed results
is not evidence, because it cannot prove that the model is always
right, only that it was right in that instance. Existing computer
models treat clouds simplistically and unrealistically, and omit
the effects of cosmic rays on clouds, so we cannot begin to be
confident that they might approximate reality.
Western governments have spent $50b on global warming since
1990, yet have found no evidence. We are constantly bombarded
with evidence that the world has warmed. Don't you think we would
have heard all about any evidence that carbon emissions
cause global warming, if there was any?
Thirdly, the warming trend that started in 1975 ended in 2001.
The global temperature has been flat since 2001, and has dipped
sharply in the last few months. The warmest recent year was 1998.
This is a very different picture from that presented by the IPCC
in 2001, of overpowering warming due to carbon emissions for
the foreseeable future. Obviously there is some other influence
on global temperatures at work, more powerful than our carbon
emissions. The IPCC are silent on what those causes might be
(hint: probably something to do with clouds).
So why do some people say temperatures are still rising, apart
form being out of date? Satellite data is the only temperature
data we can trust, but it only goes back to 1979. The satellites
go around 24/7, measuring the temperature across broad swathes
of the world, everywhere except the poles. Three of the four
world temperature records use satellite data partly or exclusively,
and they all say that the world stopped warming in 2001 and that
temperatures have recently dipped.
NASA GISS, the home of the global warming scare, only uses
land based thermometers (and a few ocean thermometers)-despite
being a space agency. Land thermometers are housed in little
boxes a few feet off the ground. They were mainly put in place
decades ago, on the outskirts of towns or cities so it was convenient
to go and read the temperature each day. But urban growth has
changed the microclimate around many of these thermometers, due
to concrete, asphalt, vegetation changes, houses, air conditioners,
and so on. In contrast to the satellite data, NASA GISS reports
a continued warming trend since 2001. But their data is likely
just measuring urban growth around some of their thermometers.
Fourthly, we looked for the greenhouse signature and could
not find it. Each possible cause of global warming heats the
atmosphere in a different pattern. Increased greenhouse warming
causes a hotspot 10 km up over the tropics. The hotspot is central
to our understanding: if there is no hotspot then either there
is no significant increased greenhouse warming, or we don't understand
greenhouse and all our climate models are rubbish anyway.
Decades of measurements with thermometers in weather balloons
have been unable to find even a small hotspot. So we now know
for sure that carbon emissions are not a significant cause of
the recent global warming. I would switch back to being an alarmist
if we had found a strong greenhouse signature. (By the way, our
carbon emissions have no doubt caused some underlying
warming, but not enough to create a hotspot that we have been
able to detect so far.)
These four changes have rendered our current debate over carbon
emissions obsolete. The changes occurred slowly as the science
on each item became more settled, so there was no sudden news
flash to make us sit up and take notice.
But now that we are finally coming to terms with how expensive
it will be to cut back our carbon emissions, the causes of global
warming have suddenly become a topic of major economic importance.
Policy makers must grapple with the possibility that global
temperatures don't rise over the next decade, and that the recent
rises were predominately not due to our carbon emissions. Deliberately
wrecking the economy for reasons that later turn out to be bogus
hardly seems like a recipe for electoral success.
Obviously the onus is on the Government
to clearly set out the evidence for believing carbon emissions
are the main cause of global warming before embarking on an ETS.
Three related articles may be located here:
The Missing Greenhouse Signature, Links to Evidence and Show us the Evidence, Penny Wong!
A brief biographical statement about
David Evans may be found here.