Valid Climate Change Models
We are interested in climate change for two reasons: 1) to adapt to changes occurring naturally and 2) to control the detrimental effect we humans might have on climate. Personally I believe in climate change and the effect of humans on climate as the historical record supports those beliefs, but cannot support the extreme measures some have proposed. One should use alternative energy sources, when it makes economic sense, and if one wishes, when it does not. Society may offer subsidies, but the case for large scale changeovers has not yet been made. Other issues, such as diseases, malnutrition, immunization, water quality, waste management, and so forth, have more proven urgency and benefit.
While I’m not a climate scientist and don’t pretend to be one, that doesn’t mean that I shouldn’t question the science behind large scale economic and climate interventions. For instance, contrary to popular believes in ancient times no one believed in the Earth was flat, while everyone knew the Sun revolved around the Earth. “Hey, I can see the ship appear over the horizon top down,” versus “I’m standing still, the sun is moving.” Until poor born-too-soon Galileo disagreed, whose case he lost because he couldn’t provide the proof that would emerge too late for him 200 years after his death. Now I’m no Galileo trusting in my theories, I require some proof of what might turn out to be true, or not.
Not being a climate scientist, I cannot asses the internal workings of their models. There are, however, two things which I can question: 1) the time frame considered, and 2) the factors included.
The first purpose to predict natural changes requires a longer time series than the second purpose to control our influence. There should be some overlap when humans had little effect, probably not all the way back to the advent of agriculture, several thousand years seems reasonable to establish a model covering natural change before human interference became significant. Modeling shorter time periods, such as couple hundred years, makes me suspicious that the influence of natural factors has not been established.
Here are some things scientists have proposed that might influence climate.
Lone Term Factors: We should be cautious when comparing current climate to that of very distant times under different conditions.
- The Milky Way. Our solar system rotates around our galaxy every 250 million years, passing through areas of dense and sparse electro-magnetic fields, radiation, dust and who knows what else. This influences the number of cosmic rays that penetrate our atmosphere, producing clouds which influences the temperature of the Earth. Time scale, millions of years, perhaps tens of millions. The link between cosmic rays and cloud formation is well established, as is the link between cloud cover and the reflection of solar energy, water vapor being the most important greenhouse gas.
- Tectonic change – The original unified land mass, Pangea, broke up pieces creating continents and islands separating waters into oceans and seas, connected by straits thereby altering wind patterns and ocean currents, influencing climate, probably huge initially, but now slower incremental change. Time frame, again millions of years. Very different conditions.
- Massive volcanic activity – The collision of tectonic plates produced cataclysmic volcanic activity, such as the Deccan planes, the rise and fall of mountain ranges etc. Time frame – millions of years.
There may be others, of which I am unaware.
Ongoing Shorter-Term Factors
- Ongoing Volcanic activity emits varying amounts of greenhouse gases and particulate matter. Time frame constant.
- Rogue Volcanoes – sporadic eruptions such as Krakatoa inducing the year without a summer are thankfully short-lived, if significant. Time frame- years.
- Ocean life – miniscule ocean creatures make shells using carbon die, sink to the bottom, sequestering carbon, and creating limestone. The amount of carbon removed from the atmosphere over hundreds of millions of years is unbelievably large. Time frame constant.
- Ocean currents such as the Gulf Stream are part of a larger system of ocean currents taking decades to circulate.
- Other Chemical processes – warming and cooling of the ocean absorbs and releases other greenhouse gases, such as methane deposits
- Milankovitch cycles –
- Our wobbly Earth spins like a top slowing down while rotating around the sun in a path that alternates between an ellipse and circle over 95,000 years. The amount of solar energy received varies reportedly as much as 20% between summer and winter depending in the shape. Currently the path is almost a circle producing a difference of 6%.
- The tilt of the earth varies between 21.5 and 24.5 degrees over 41,000 years accentuating and dampening the seasons. Note that the tilt cycle at 41,000 years is not in sync with the 95,000 year cycle of eccentricity. Consequently, sometimes the northern hemisphere will lean towards the sun when close, and sometimes away. Currently the north pole tilts away from the sun in summer. Because the northern hemisphere has more land than the southern hemisphere, which carries differences in the load of solar energy carried versus rejected thereby influencing climate.
- Over 23,000 years the Earth wobbles pointing towards Polaris or Vega. Currently our summer occurs when the earth is almost at its farthest from the sun, in another 10,500 years summer will occur when the earth is closest to the sun, producing warmer summers and colder winters. Thus we should expect gradually warming summers and colder winters.
- Solar cycles – NASA published a report relating a .2% change in solar output to 25% of recent temperature change.
- Most of us are familiar with the 11-year sunspot cycle. Contrasted with the visibly dark sunspots of relatively low solar output are invisible hot spots of high solar output. The absence of sunspots is associated with low solar output. Some periods are more extreme in a cycle of 350-400 years.
- Solar physicist Valentina Zharkova has related the movement magnetic fields of the two solar north poles and two solar south poles influencing the magnetic field of the solar system, varying cosmic ray penetration with consequent cloud formation, temperature changes and so forth. This is an evolving area of research.
- While the earth rotates around the sun, the sun rotates around the center of the solar system which is not located at the center of the sun. The sun rotates around this center in a circle with a cycle of 2,100 years moving closer to earth and away while the earth is likewise moving closer and further away. Again, out of sync, so sometimes there will be more solar energy delivered and sometimes less. The next 500 years, the sun will move closer to the earth during summer, and further away in the winter, making summers warmer in the northern hemisphere and colder in winter, vice versa in the southern hemisphere, cooler summers and warmer winters.
- Solar Irradiance – are all the wavelengths imparting energy included.
- Humans effects – burning of wood, coal, gas, and oil; practice agriculture and husbandry; emergence of megapolis, and so forth.
To my knowledge, current climate models assume solar input is constant and cover short time periods rather than the thousands of years that IMHO would appear exhaustive given the major climate changes since the last Ice Age and the advent of civilization. Much work remains to be done.
As to the factors listed above, Judith Curry https://judithcurry.com/2020/02/13/plausible-scenarios-for-climate-change-2020-2050/ considered four major factors in great detail:
- Man Made Emissions
- Solar variations
- Volcanic eruptions
- Decadal-scale ocean circulation variability
Curry appears to have completed the most comprehensive review of factors influencing climate in the near term.