I watched a programme last night on BBC2 called “Horizon” about global warming. Originating from the BBC it was inexorably transparently bias
right from the offset and the so-called scientist presenting the programme rebutted every argument against AGW by “argument from consensus”, much
to James’ Delingpole’s chagrin. He selected poor representations on our behalf. He summarised sceptics’ arguments feebly, then attacked those
summaries and even went as far as to defend Phil Jones’ apocryphal methodology of splicing tree-ring data with instrumental data after they diverged
post-1960. In the programme a number of scientists said that we are currently experiencing dramatic temperature increases as well as unprecedented CO2
levels. In this thread I’m going to present some paleoclimatological data spanning back 600 million years, as well as some instrumental data
spanning back around 300 years to see just how dramatic the 20th century temperature rises have been and how “unprecedented” current CO2 levels
So, without further ado, let’s take a look.
(Scotese 1990 - temperature and Berner 2001) Source.
The graph above of rock-sediment paleoclimate data shows the earth’s temperature and CO2 levels going back 600 million years. The first thing that
strikes me about this graph is that CO2 and temperature appear to rise and fall completely independent of one another. There is no clear correlation.
Furthermore there appears to have been glaciations during the Ordovician Period when CO2-levels were supposed to have been very high (at around
4500ppm, today’s concentration stands at 388ppm) and at the start of the Carboniferous when CO2-levels appear to have been steady. According to
“life flourished” during the Cambrian under the super-high concentrations of
CO2, so dramatically that it is called the “Cambrian Explosion”. And it wasn’t just plant life that flourished but animal-life too. So much for
the alleged lethal toxicity of CO2 at 5,000ppm. Today we currently live in a CO2-impoverished environment.
Unlike the rock-sediment data the graph above of ice-core measurements show a very good correlation between CO2 and temperature. In his film ‘The
Inconvenient Truth’ Al Gore says that the relationship between CO2 and temperature is “complex” and misleadingly suggests in his movie that
ice-core paleoclimate data supported the idea that CO2 controls temperature. You can see him with his nice graph below conveniently leaving
temperature and CO2 separate.
If Al Gore had have put CO2 and temperature together it would have been obvious to anyone that there is an average 800-year time-lag for the
atmospheric CO2 concentration to start rising after a time of significant warming. (800 years ago the world was in the Medieval Warm Period so we
should expect CO2 to be rising now in any case).
Zooming in on the ice-core data this is what the 800-year-time-lag looks like.
Another thing Al Gore failed to mention is something called “diffusion”. CO2 being a soluble gas means that it would inevitably leak out of the
trapped air-bubbles in the ice thereby underestimating true values present thousands of years ago. For a fuller explanation on “diffusion” and
references on changes in the chemical-composition of gases trapped in air-bubbles see this
Other paleoclimate data, like Stomata, shows CO2 has been considerably more variable than what is depicted in the ice-core data. See graph below. As
Dr Roy Spencer explains “Keep in mind, very old ice core measurements come from highly compressed layers. How much diffusion of CO2 has there been
across these thin layers of ice over thousands of years? Anything like what we have measured at Mauna Loa over the last 50 years would be smoothed
out, giving the appearance of stable CO2 concentrations over centuries or millennia”. Also, in the ice-core data above we can see that the earth
follows a natural and predictable pattern of interglacials lasting about 15,000 years separated by comparatively longer ice-ages lasting approximately
100,000 years. We currently live in the Holocene interglacial period. According to the ice-core data, the last interglacial period, known as the
‘Eemian’ was much warmer than today’s temperatures. In fact the last three interglacials were as you can appreciate from the graph above.
Therefore is it any wonder that temperatures are rising? After all it is what we should expect in an interglacial and considering we have just emerged
from a mini ice-age 300 years ago (called the ‘Little Ice Age’, of which we are still recovering).
Above is a graph showing CO2 levels from Stomata paleoclimate data. There are of course uncertainness with Stomata proxies, just as there is with all
paleoclimatolgical data, but they do appear to agree with flask-measurements. If the graph above is an accurate representation of CO2 levels over the
past 15,000 years then the current concentration of CO2 is not anything unusual.
The graphs above (which are the same - just different sizes) are from the Central England Temperature Record (CER) over the last 300 years (the oldest
instrumental temperature-record we have). Two things interest me about this graph. Firstly, it shows that the temperature increased by 2.2C in just 36
years from 1698-1734. Compare that to the 0.3C-0.4C increase in temperature that the CER have measured over the last 30 years as we’ve been
unremittingly and unremorsefully pumping out CO2. The temperature increase during 1700 was five times the size! The increase was much greater than
what man has apparently been responsible for over the last 30 years. We are clearly well-inside natural variation. Secondly, CO2-emissons appear to
have had no appreciable effect on the temperatures post-1945. One could argue that it is regional and not global. As if CO2 would geographically
discriminate? Nevertheless, let’s take a look at the global temperature-record over the last 150 years as measured by HADCRUT3.
The graph above is from HADCRUT3. It shows over the last 150 years that we have had three warming periods lasting between 20-30 years separated by
cooling periods lasting between 15-30 years. From 1905-1942 there was a temperature increase of approximately about 0.35C. Take note that this
temperature increase was before we started burning hydrocarbons in large quantity post-1945. From 1945 to the present day we have emitted
approximately 80% of all our carbon emissions. Therefore if CO2 was the main cause of global warming in recent times we should expect the temperature
to have accelerated as our emissions of CO2 have increased. However this is clearly not the case. The temperature increase from 1970-1998 was only
approximately 0.35C. They are, in other words, more or less the same. The trends are as follows:
Period - Length Trend - (Degrees C per decade)
1860-1880 ------ 21 ------ 0.163
1910-1940 ------ 31 ------ 0.15
1975-1998 ------ 24 ------ 0.166
1975-2009 ------ 35 ------ 0.161
Even Phil Jones admitted in a BBC interview
that these two periods are not, in his own words
“statistically significantly different from each other”. Thus, we can see that the warming since we started burning hydrocarbons has not been
dramatic or outside of natural variation. Mother earth appears to be simply rolling on with natural cycles as she has done for millennia.
on 25-1-2011 by Nathan-D because: (no reason given)