Climate Change Factors, Planetary Cycles

Skeptical about "global warming" and climate change? You should be. Man-made pollution is an environmental issue worth addressing, but we also need to consider factors that are outside of our scope of influence, such as Milankovitch Cycles.

http://video.nationalgeographic.com/video/national-geographic-channel/shows/naked-science/ngc-ice-age-cycles/

What are Milankovitch Cycles? Natural global warming, and cooling, is considered to be initiated by Milankovitch cycles. These orbital and axial variations influence the initiation of climate change in long-term natural cycles of 'ice ages' and 'warm periods' known as 'glacial' and 'interglacial' periods. The cycles appear to be range bound in the paleo record for the past 5 million years. Our current climate forcing shows we are outside of that natural cycle forcing range. 


The natural cycle that people refer to regarding large scale climate change is the time between ice ages and warm periods. The long cycle time is about 100,000 years. We can spend around 20% of the cycle in an interglacial and around 80% in an ice age, depending on where we are in these cycle influences.

These include orbital gravitational forcing caused by the movement of other planets in our solar system. In other words the mass and movement of the other planets in our solar system actually affect the earth orbit just as our planetary mass similarly affects their orbits. This pushing and pulling actually changes our orbit around the sun..., the tilt of our axis..., and the wobble of our axis.

When those factors bring us closer to the sun long enough, and at an optimal angle for increased heating on earth, the ice melts quickly, the sea level rises about 400 feet, and we enjoy a warm period 'like' the one we are in now. That is the natural cycle, brief warm periods followed by an ice age about every 100 thousand years.

There are three general factors that determine the forcing changes in the Milankovitch cycles.

1. Eccentricity (the elliptical changes in the earths orbit around the sun)
2. Obliquity (the tilt of the earths axis toward and away from the sun)
3. Precession (the wobble of the earths axis toward and away from the sun)

http://ossfoundation.us/projects/environment/global-warming/milankovitch-cycles

It is worth considering that reducing pollution would increase the quality of our ecosystem, but a complete cessation of the creation of all of those pollutants which have negative effects would not likely have a significant change on the warming and cooling cycles that are a result of the wobble of the Earth's rotation.

The tilt of the earth relative to its plane of travel about the sun is what causes seasons. The hemisphere "pointing toward" the sun is in summer, while the opposite hemisphere is in winter. The earth makes one full orbit around the sun each year. The northern hemisphere is in summer in the left image, while 6 months later, the southern hemisphere has summer, as in the center image. If the earth's axis were "straight up and down" relative to the orbital plane, as in the right-hand image, there would be no seasons, since any given point at the top of the atmosphere would receive the same amount of sun each day of the year. 

Changes in the "tilt" of the earth can change the severity of the seasons - more "tilt" means more severe seasons - warmer summers and colder winters; less "tilt" means less severe seasons - cooler summers and milder winters. The earth wobbles in space so that its tilt changes between about 22 and 25 degrees on a cycle of about 41,000 years. It is the cool summers which are thought to allow snow and ice to last from year to year in high latitudes, eventually building up into massive ice sheets. There are positive feedbacks in the climate system as well, because an earth covered with more snow reflects more of the sun's energy into space, causing additional cooling. In addition, it appears that the amount of Carbon Dioxide in the atmosphere falls as ice sheets grow, also adding to the cooling of the climate. 

The earth's orbit around the sun is not quite circular, which means that the earth is slightly closer to the sun at some times of the year than others. The closest approach of the earth to the sun is called perihelion, and it now occurs in January, making northern hemisphere winters slightly milder. This change in timing of perihelion is known as the precession of the equinoxes, and occurs on a period of 22,000 years. 11,000 years ago, perihelion occurred in July, making the seasons more severe than today. The "roundness", or eccentricity, of the earth's orbit varies on cycles of 100,000 and 400,000 years, and this affects how important the timing of perihelion is to the strength of the seasons. The combination of the 41,000 year tilt cycle and the 22,000 year precession cycles, plus the smaller eccentricity signal, affect the relative severity of summer and winter, and are thought to control the growth and retreat of ice sheets. Cool summers in the northern hemisphere, where most of the earth's land mass is located, appear to allow snow and ice to persist to the next winter, allowing the development of large ice sheets over hundreds to thousands of years. Conversely, warmer summers shrink ice sheets by melting more ice than the amount accumulating during the winter. 

What is The Milankovitch Theory?  

The Milankovitch or astronomical theory of climate change is an explanation for changes in the seasons which result from changes in the earth's orbit around the sun. The theory is named for Serbian astronomer Milutin Milankovitch, who calculated the slow changes in the earth's orbit by careful measurements of the position of the stars, and through equations using the gravitational pull of other planets and stars. He determined that the earth "wobbles" in its orbit. The earth's "tilt" is what causes seasons, and changes in the tilt of the earth change the strength of the seasons. The seasons can also be accentuated or modified by the eccentricity (degree of roundness) of the orbital path around the sun, and the precession effect, the position of the solstices in the annual orbit. 

What does The Milankovitch Theory say about future climate change?

Orbital changes occur over thousands of years, and the climate system may also take thousands of years to respond to orbital forcing. Theory suggests that the primary driver of ice ages is the total summer radiation received in northern latitude zones where major ice sheets have formed in the past, near 65 degrees north. Past ice ages correlate well to 65N summer insolation (Imbrie 1982). Astronomical calculations show that 65N summer insolation should increase gradually over the next 25,000 years, and that no 65N summer insolation declines sufficient to cause an ice age are expected in the next 50,000 - 100,000 years ( Hollan 2000, Berger 2002).

http://www.ncdc.noaa.gov/paleo/milankovitch.html

Naturally-occurring water vapor is the greatest abundance of greenhouse gasses (over 99%) though it's effects are different from CO2 or SO2, so even a complete cessation of burning fossil fuels would be a minor effect on the climate change.

The issue with water vapor in regards to the Milankovitch cycle is that it creates a positive feedback loop, all without human interaction, just as it has done for many cycles, even before humans existed to burn fossil fuels. You can see it in the cycles, the temperature synced with the greenhouse gasses. Water vapor enters the atmosphere, global temperatures rise, ice caps and glaciers melt, more water vapor enters the atmosphere, global temperatures rise, and on and on...

Certainly, I strongly believe that it would be a positive move to reduce pollution for the sake of air and water quality, but learn to adapt to a changing world. Darwin would be disappointed if we didn't even grasp that concept...

Even volcanic eruptions are not all bad, but I think that some people have a hard time looking at an issue from a larger scale. Climate change is one of those issues. Many counter points seem to be dismissed easily in the hunt for the global warming boogeyman. It's like the financial crisis, we can't stop it, so it's best to minimize damage and adapt to the outcomes.

I find it to be hubris that some humans believe that our actions are more significant than those of the planet and it's natural processes.