As the Bali Climate Change Conference goes on, there is still far too much quibbling over whether anthropogenic global warming even exists. All of this back and forth is costing valuable time, and causing an incipient problem that might be at least partly corrected, to metastasize to a possibly ungovernable situation - perhaps even a "runaway Greenhouse effect" and transformation of Earth to another Venus within 1ka (one thousand years).
The inherent problem with most skeptics lies in their carelessly invoking “natural warming” cycles – which simply don’t hold up to investigative scrutiny – in terms of the magnitudes of energy input required for the level of warming observed the past century.
Solar physicist John Eddy, who made it is research specialty to study long-term solar variations connected to climate change, noted the period of 12th century warming in his book, ‘The New Solar Physics’, AAAS Selected Symposium, Westview Press, 1979, p. 17.
Eddy noted that this coincided with a period of higher solar activity (i.e. more sunspots) and possibly greater luminosity – on account of the fact that the irradiance is amplified around sunspots owing to redirection of convective heat flow. (Bear in mind the plasma in spots is at lower temperatures, by about 1500C, because of the powerful magnetic fields in them).
During solar cycle 20 – when I also conducted investigations on solar flares and their effects- the then Solar Max satellite used an active cavity radiometer (ACRIM) to measure temperature increases arising from higher activity – especially as generated by more convection at the periphery of large spots. The differential was something on the order of 0.1C at the Sun! Since the radiant energy must now transit 150 million kilometers, and its intensity falls off as the inverse square, one can see this would translate into negligible increases at Earth.
What about longer period increases in solar luminosity associated with its possibly being a variable star – as opposed to sporadic sunspot outbursts?
The maximal magnitude of inherent solar -induced climate variability was probably first highlighted by Sabatino Sofia et al in their paper Solar Constant: Constraints on Possible Variations Derived from Solar Diameter Measurements, in Science, Vol. 204, 1306, 1979. Their estimate was a solar change in irradiance of roughly 0.1 % averaged over each solar cycle. (Irradiance is a measure of the energy per square meter received from the Sun).
Thus – if the solar irradiance effect at Earth (solar constant) is normally about 1360 watts/m^2, this would imply an increase of roughly 1.36 W/m^2.. The problem is that there is no observational evidence to support this in the warming period of the 12th century, or any time in the past century – when global warming spiked to serious levels. (Some like Sofia have argued that even if it had occurred, it would only engender a temp. increase contribution of perhaps one-fourth of one degree, or significantly less than what has been documented.
More recent space-based observations appear to show a variation in solar irradiance of at least 0.15% over the standard 11-year solar cycle. (E.g. Parker, E.N., Nature, Vol. 399, p. 416). However, even with this higher percentage ascribed to solar changes, the heating effect is nowhere near comparable to that induced from man-made global warming. (See, e.g. Martin I. Hoffert et al, in Nature, Vol. 401, p. 764).
As the authors in the latter study point out, the heating component arising from greenhouse gas emissions from 1861-1990 amounted to anywhere from 2.0 to 2.8 watts per square meter. The solar variability component detected over the same period amounted to 0.1 to 0.5 watts per square meter. Thus, even the MAXIMUM solar variability amounted to only a fraction (25%) of the MINIMUM power input from human-induced greenhouse warming!
Most serious climate researchers (such as Gunther Weller – who was at the University of Alaska, Fairbanks when I was there) already believe we're in the first stages of a positive feedback, non-linear effect that is leading right into the maw of the runaway greenhouse. Though most will not own up to it publicly for fear of raising alarm.
The basis has already been described by Sagan and others: Melting of ice caps (already occurring) results in diminished albedo (reflection of solar radiation back into space), and a darker Earth surface - with more IR (infrared or heat energy) absorbed - enhancing global warming. At the same time global warming is accelerated in the oceans, and both El Nino and La Nina are ramped up in the unfolding panorama of global warming (cf. S. George Philander in Eos, March 31, 1998, ‘Who is El Nino?’) . In the meantime, we have new evidence that the melting permafrost (e.g. in Alaska) is releasing 25- 100 times more greenhouse gas as methane and CO2.
As more ice melts from the polar regions, positive feedback proceeds faster. The overall (mean) ocean temperature continues to rise - ultimately becoming too hot for any marine life- and reaching equilibrium temperature somewhere in the next 500 years. All ocean currents, circulation systems will, of course, cease. With atmospheric circulation soon following (as on Venus) , all solar energy going into heating the oceans until their specific heat capacity is reached.
Of course, long before this we will be in a state of emergency. When I was at the Geophysical Institute in Fairbanks, AK I used to chat with some of the Atmospheric scientists there. Almost all agreed that what we may have on our hands will be many times worse than the Luis Alvarez' proposed extinction asteroid impact of 65 million years ago.
People - when they talk blithely and ignorantly of 'adjusting' simply have no idea of how bad it can get. Or that a 'runaway greenhouse' (such as converted Venus to a hellhole) is more than possible. Can they 'adjust' to global mean air temperatures of 60 C (yes, that's Celsius degrees)? I don't think so, especially as all the oceans will have boiled away!Yet, this is our inevitable fate if we don't get a handle on the problem RIGHT NOW. Before the 'runaway' sets in when CO2 starts to be 'out-gassed' from the oceans, and all the trillions of tonnes of carbonate rocks on the planet.
Long before that, of course, a host of exotic diseases will have spread across the world and wrought havoc - and all the fools clamoring for warm temperatures will wish otherwise with the first case of amoebic dysentery or dengue hemorrhaghic fever. Especially as we're already losing efficacy of anti-biotics from over-use(See, e.g. Global Climate and Infectious Disease: The Cholera Paradigm, in Science, Vol. 274, 20 December, 1996, p. 2025.)
And I won't even go into the tech predictions of regularly fried power-grids because so many teeming millions are trying to keep cool.
The late Carl Sagan noted in a CNN interview (with Ted Turner) ca. 1989 (still have it on tape) that the limits for catastrophic climate change- we're talking species exterminating magnitude- are not as high as many think. In fact, he cited the tolerance increment of six degrees Celsius. When global mean temps. veer past that, watch out. Right now - from all data collected- we appear to be approaching a 2 degrees Celsius increase, possibly more, by 2100.
Even if we initiated massive emissions cutbacks today it may be inadequate, since the carbon dioxide deposition time (time for it to remain in the atmosphere and create problems) approaches 100 years, as Sagan (and others) have also noted. Thus, the climate change we're seeing NOW, is really traceable to the conditions of CO2 concentration from ca. 1903!!!Our CO2 inputs, will become recognized ca. 2103. And be added to the cumulative total at THAT time..
Now, while not everyone yet agrees we are in such an emergency – most climate scientists of any repute argue that we cannot afford the luxury of waiting any longer for “absolute proof” to arrive. We must act now to initiate credible policy changes (not merely exchanging "carbon credits") or face dire consequences – and have future generations curse us forever for our inertia and inaction.