Much of the blogospheric discourse on climate is for me a circle of hell undiscovered by Dante. It is a circle ruled over by Humpty Dumpty and where words mean whatever he says they mean. You can feel the planet shifting randomly under foot. “The question is,” said Alice, “whether you can make words mean so many different things.” Looking over the short note on climate matters by John Reid that was promoted on Quadrant Online recently – it is very clear that a collection of notions do not a valid scientific inference make. Ultimately in science words are not sufficient and truth is founded on experiment.
In January 1859, John Tyndall began studying the radiative properties of gases. He constructed the first ratio spectrophotometer. The device uses a reference and an experimental heat source that passes radiant heat through a tube which was then filled with various gases. It was inspired by speculations of some of the leading minds of his time. The results were a bit of a scientific revelation – and the scientific origins of global warming.
“The bearing of this experiment upon the action of planetary atmospheres is obvious … the atmosphere admits of the entrance of the solar heat, but checks its exit; and the result is a tendency to accumulate heat at the surface of the planet. John Tyndall.
John Reid instead discusses Rachel Carson and nuclear fallout. It may in fact be the origin of social movements – who later looking for a cause to justify their existence took on global warming. These groups take the art of a narrative superficially in the objective idiom of science to extraordinary heights. But it is the science – and not forebodings of millennialist doom – that is apparently in question.
Charles Keeling began monitoring carbon dioxide in Hawaii in the 1950’s. Just after both the emission of greenhouse gases commenced increasing dramatically as the post war boom took off – and the planet started cooling. Increasing carbon dioxide in the atmosphere should – all things being equal – result in warming. It is obvious in retrospect that something else was happening – something now known as ‘internal climate variation’. It is a change in cloud, ice, vegetation, wind, currents and biology that proceeds much faster than the trigger event. Some small change in the system – according to chaos theory – initiate sizeable changes as tremendous energies cascade through powerful sub-systems. Tipping points are a reality seen in climate data.
The planetary cooling from the mid 1940’s was most clearly associated with a shift in the Pacific Ocean to more cold water upwelling in eastern Pacific. A cool sea surface temperature in the north-east Pacific and more frequent and intense La Niña. This reversed in 1976/77 – and the renewed warming sparked renewed interest in the work on radiative properties of gases and the measurements of Charles Keeling. There is a shift in the Pacific state every 20 to 30 years. It explains the temperature pause since 1998.
But while there is internal variability some fundamentals of greenhouse gases are clear. Carbon dioxide is a greenhouse gas. We are adding carbon to the Earth system at some 10 billion tonnes per year. Carbon dioxide concentration in the atmosphere is increasing. A change in outgoing longwave radiation has been observed from space. We may infer on a solid empirical foundation that – all things being equal – anthropogenic carbon dioxide is warming the planet. What is done with that knowledge is not a matter for science alone. There are many policy options that make far more sense than spending trillions of dollars on renewables.
The Earth is not really a greenhouse. Greenhouse gases don’t block all outgoing radiant energy – it merely slows it down by capturing more infrared photons and re-emitting in all directions including down – increasing net energy retained at any instant in the atmosphere. At the edge of space – all energy is lost as radiant energy or as reflected visible light.
Latent heat plays a part in the troposphere – the bottom 6 to 10km of the atmosphere – as warm, moist air rises it cools, water vapour condenses and heat is released. As it rises the parcel of air loses energy and expands until the temperature is the same as the surrounding air. This indeed explains most of the difference between surface and satellite temperature records. Thermometers measure sensible heat at the surface. Satellites measure all heat in the troposphere – which is most of the heat in the atmosphere. Drought changes the balance of sensible and latent heat at the surface. Surface temperatures are higher when there is less water and less evaporation – skewing surface temperature records. Latent heat is however just one of the processes influencing the temperature profile of the atmosphere. It is nowhere near as simple as decreasing temperature with altitude. Energy flow is predominantly from the Sun to the surface to the atmosphere and into space. As altitudes increase proportionally more energy is radiated to space.
While one can discuss a process or two – putting them all together to make a coherent model of our massive and turbulent planet requires supercomputers. I’m not speaking here of the IPCC ensembles of opportunity – which is ultimately a very silly procedure. Models start with a vertical and horizontal grid and nonlinear partial differential continuity equations. The equations conserve momentum, mass and energy across grid boundaries. There are many diverse limitations on models – computer power and grid size, processes that happens at sub-grid scale and how well they are defined, how well known the starting point or boundary conditions are, etc. Just as weather forecasts are useful for a week or so until too many errors accumulate – it may just be possible to build a climate model that is useful for seasonal to decadal forecasting. And for exploring in a quantified way the interactions of the many Earth processes. It would be a shame to throw the baby out.
“There is a new perspective of a continuum of prediction problems, with a blurring of the distinction between short-term predictions and long-term climate projections. At the heart of this new perspective is the realization that all climate system predictions, regardless of time scale, share common processes and mechanisms; moreover, interactions across time and space scales are fundamental to the climate system itself. Further, just as seasonal-to-interannual predictions start from an estimate of the state of the climate system, there is a growing realization that decadal and longer-term climate predictions could be initialized with estimates of the current observed state of the atmosphere, oceans, cryosphere, and land surface.” Hurrell et al, 2009
Until then we are constrained to the scientific basics – except for the many who aren’t. As the atmosphere warms the planet loses exponentially more energy according to fundamental physical principles. As water warms more evaporation occurs carrying energy higher in the troposphere where it can be lost more easily – but there are considerations of wind speed and atmospheric humidity. As more water vapour condenses at altitude – more clouds form reflecting sunlight back into space and cooling the planet. Although there is little to no evidence of changing total rainfall and clouds seem to respond more to changes in sea surface temperature. An animal of a different kind. Warming results in more carbon dioxide release from soil and peat moss – it is some 20% of the fossil fuel emissions. Oceans are carbon sinks on balance in processes that return carbon to the Earth’s interior. Increases in carbon dioxide and equilibrium chemistry outweighs very small changes in solubility. But both spatial and temporal variability is huge. A seasonal squiggle in the ever increasing carbon dioxide curve is pronounced in the Northern Hemisphere and muted in the Southern. It is the waxing and waning of biological activity in the bigger land area of the Northern Hemisphere. None of these processes can be said unambiguously to negate global warming. For the most part there is a lack of observation and quantification which is where real science starts. For teaching children we need to teach the building blocks of empirical science – but certainly without emotional baggage. There is nothing scientific about tales of climate doom.