Last week, I wrote about the perception chemists have of the way people see chemistry. We generally perceive the public as being much more negative than they actually are.
This attitude is not confined to chemists as most scientists see the public as being much more negative about science than they actually are.
On the whole, people generally appreciate science and scientists.
And although they don't necessarily understand the science, they appreciate what scientists do.
They also understand science is important.
This is why issues such as climate change are such a conundrum.
The science is complex.
It comes from many disciplines. It requires a synthesis of knowledge. It is not something that can be summed up in a 30 second sound bite on the evening news.
Hence, I have been writing about the subject for almost two decades.
Each time, I try to present a few more of the facts.
Sometimes I recap what has already been presented.
Sometimes it is clear there is still a significant misunderstanding of the basic science.
With that said, carbon dioxide is a molecule.
It is a simple molecule consisting of two oxygen atoms bound to a central carbon: O=C=O. It is linear but not rigid.
Think of it as being like three excitable children connected by springs.
As a consequence of its structure and flexibility, the molecule both vibrates or stretches back and forth and it also bends into a V-shape.
The atoms are in constant motion, like excited children.
It also rotates and moves through space.
All of this motion requires energy.
Vibrations and bending involves the absorption of energy in the infrared region of the electromagnetic spectrum. Rotation involves microwaves.
Chemistry tells us the vibration and bending of the molecule means only narrow bands of infrared radiation are absorbed.
There are quantum mechanical effects involved but carbon dioxide does not absorb the whole infrared spectrum.
Nor is carbon dioxide the only molecule in the atmosphere that absorbs infrared radiation.
Water, methane and even oxygen are also capable of absorbing heat.
Further, the absorption of heat by these gases is not limited.
It is not logarithmic.
It is not capped.
Add more carbon dioxide and more infrared radiation will be absorbed.
The temperature will go up.
The upper limits to atmospheric heating are seen in the atmosphere of Venus where carbon dioxide is 96 per cent of the atmosphere.
Venus has the highest average surface temperature of all the planets - 462 Celsius - even though Mercury is much, much closer to the Sun.
On Venus, we can see a runaway greenhouse effect.
Visible light can enter the atmosphere unimpeded.
It is not absorbed by the gases on the way in but the re-radiated heat from the surface is trapped on its way out. The result is an unbearably hot world.
In our atmosphere, carbon dioxide is only present at 400 parts per million.
It is not the only gas responsible for heating the air.
Still, even 400 ppm of carbon dioxide is enough to have an effect on the atmosphere.
This is particularly evident as carbon dioxide levels have increased by 120 ppm over the past 150 years - 80 ppm of which has happened in the last 50 years, according to the U.S. National Oceanic & Atmospheric Administration.
And yes, the level of carbon dioxide has generally fluctuated over geological time periods, as has temperature.
However, the data we presently have has led atmospheric scientists - along with many other scientists - to conclude there is a causal relationship between the increasing mean surface temperature of the planet and the levels of carbon dioxide in the atmosphere.
It is complex.
There are many variables involved such as the amount of water vapour in the air, the overall albedo -amount of light reflected from the surface -of the planet, ocean currents, the rate of carbon dioxide exchange, the extent of plant coverage, etc.
Further complicating matters is the variability in the data.
Measurements made by instruments have inherent levels of error but there is also the intrinsic variability in the data itself.
For example, measuring the temperature at the airport, downtown, and UNBC at the same time on the same day can give three different answers.
They won't be widely different but they will have slight variations.
Which one is right?
They all are so to get a proper map of temperature, we need to use statistical analysis.
But sorting through all of the data and untangling all of the information provides a clear picture.
We know carbon dioxide absorbs infrared radiation.
We know it is much more effective at absorbing heat than some other gases, such as oxygen.
We know carbon dioxide affects the flow of heat from the surface of the planet into outer space.
That is, we know carbon dioxide is involved in the rate of heat loss. And we know carbon dioxide concentrations are increasing.
Those are the facts. For most scientists, changing carbon dioxide levels in the atmosphere represent a clear threat. One that we need to address.
