We are often told that temperatures have never been as high as they are today and
that the cause is the increase in the amount of carbon dioxide in the atmosphere since
In September 2003 I was told that cores taken from the ice cap
in Greenland showed that temperatures had been well above current temperatures. With
a bit of searching on the web I found that the data was there for all to see.
The critical information from Greenland was not only that conditions
had been WARMER but that the world had also COOLED.
Scientists look at the chemical composition of the ice and the air bubbles trapped in the ice and
from these deduce the temperature and the level of carbon dioxide (and other gases).
A little more searching revealed that information about carbon dioxide levels. Data from
the Vostok site in the Antarctic goes back several hundred thousand of years and has been
The Vostok data shows that carbon dioxide levels usually rose AFTER a increase
in temperature, not before. There was no way that any increase carbon dioxide was the
cause of a rise in temperature.
This web page contains graphs of data from ice-cores that prove these statements.
Below is the graph of Greenland's temperature in the last 4,000 years.
The changes are probably very
indicative of temperatures changes across all of the Northern Hemisphere.
Temperatures from Greenland.
About 1,000 years ago average temperatures were
about 1 degree higher than today (which makes our concern about
an 0.4 degree rise since 1980 rather minor).
About 2,100 years ago average temperatures were
about 2 degrees higher than today.
About 3,300 years ago average temperatures were about 3 degrees higher
than today. (The data from Greenland ice-cores goes back far beyond this time
so despite what some people say, it looks like it takes a lot more than 3 degrees to
melt the ice cap!)
For almost all of the last 4,000 years temperatures have
been higher than today. More precisely, apart from a brief
period 1200 years ago, it is only the last 750 years that have
been at or below current temperatures. On this evidence it is more reasonable to assume
that warmer weather is the natural condition - in so far as we can claim any stability or
consistency in something that is constantly changing.
Look at the increase in temperature about 3200 years ago. It is about 1 degree in less
than 50 years. In the twentieth century temperatures have risen and fallen, the most recent change
being an increase since 1980 of about 0.4 degrees. The maximum was reached in 1998 and
while temperatures have fluctuated since then they have not exceeded that point. An increase of
1 degree in 50 years is looking very unlikely.
Here we'll look at two graphs of data from the ice cores drilled near the Vosotok base in
the Antarctic. They clearly show that changes in carbon dioxide levels were not the cause of
the increase in temperature. (There are suggestions that the increase in carbon dioxide was
actually caused by the temperature increase - which is the complete opposite to what we are
and carbon dioxide levels (1).
The scale for carbon dioxide is not shown due to the graphing
tool. Its omission is not important because the key is the
time of the turning points and the relationship of carbon
dioxide changes to temperature changes.
Working from the right (oldest) to the left (most recent) we
(a) a peak in carbon dioxide was reached at 46,000
years ago, about 2,000 year AFTER a peak in temperature
(b) a low point in temperature was reached about 43,000
years ago but carbon dioxide levels continued to fall
(c) carbon dioxide levels increases from 42,400 years ago
to 38,500 years ago almost as temperature rose, but remained
elevated for the next 5,000 years while temperatures fell
(d) temperature peaked about 32,000 years ago but carbon
dioxide continued to increase for the next 2,000 years.
(e) the changes in carbon dioxide between 20,000
and 28,000 years ago have been smooth but the changes in
temperature have been abrupt and as much as 1.5 degrees in 200
It is clear that carbon dioxide has not caused the change in temperature because
the changes in carbon dioxide have lagged behind the temperature changes.
To put it another way, something caused the changes in
temperature but it wasn't carbon dioxide.
|Another graph of temperature and carbon dioxide levels
is shown below.
Temperature and Carbon dioxide
It appears that temperature may have risen slightly before
carbon dioxide 138,000 years ago but the important fact is that
carbon dioxide levels remained elevated even as temperatures
slowly fell. In fact it took more than 15,000 years for
carbon dioxide levels to decline.
If these elevated levels
of carbon dioxide were the cause of warming when the
temperatures increased, then why did the temperatures decrease
? The only logical explanation is that the carbon dioxide
was not the cause of the warming.
Nor is it a significant cause of warming at any time.
We are also told that millions of years ago the amount of carbon dioxide in the
atmosphere was much higher than today and that the world was probably a warmer and wetter place.
Even with those higher levels of carbon dioxide there was no RUNAWAY WARMING
and so there is absolutely no justification for predictions that it can be expected today.
Let's take a look at the changes in temperature and atmospheric
carbon dioxide since 1960. To do that we use data from the
UK's Climate Research Unit (CRU), data that is readily available
via the web.
Carbon dioxide (CO2) and temperature since 1960
This graph shows the weakness in the claim that carbon dioxide - especially man-made
carbon dioxide - is the cause of warming. Carbon dioxide levels have increased steadily at
an average of 1.3 parts per million by volume (ppmv) per year with greater increase in a
few years and a smaller increase in others. At the same time temperatures have been all
over the place, increasing a lot in some years, a little in others and even falling in some.
Let's look at some specific periods...
(a) the average global temperature fell from 1960 to about 1976
even as carbon dioxide increased.
(b) the average global temperature in 1977 was 0.3 degrees
higher than the previous year and yet the increase in carbon
dioxide was steady.
(c) around 1985 average global temperatures fell but carbon
dioxide continued to increase.
(d) in 1992 the average global temperature fell below the
1983 temperature but carbon dioxide levels were 14ppmv higher than in
(c) the average global temperature is almost unchanged across
2002-2004 and it is below the temperature of 1998. Atmospheric carbon dioxide has
increased since 1998 and yet temperatures have fallen.
It is clear that carbon dioxide is not a significant cause of temperature
change because if it was, the temperature decrease in certain years would never have occurred.
If carbon dioxide has even the tiny influence of 0.7 C degrees warming for a doubling of CO2 as many
scientists claim, then other more significant forces are causing the changes in temperature.
In short, the alarmist claims about carbon dioxide are nonsense.
It would make far more sense to investigate and understand these other forces and then decide
what action, if any, is appropriate.
Millions of years ago the level of atmospheric carbon dioxide was about 5 times greater than today.
The fact that you are here to read this makes it clear that even with high concentrations of carbon
dioxide run-away warming did not take place million of years ago and so
there is no reason to suppose that it might today. The claims are just more nonsense