No Silver Bullet for Cause of Global Warming

• Debating the cause of global warming can generate passionate disagreements. No matter your stance on the issue, there are some accepted scientific theories that explain global warming and climate change. Explaining what causes global warming and how can only be addressed while considering the endless amount of feedbacks involved in our global ecosystem. Having said this, there a few major climate change players that help explain what causes global warming.
  
  

Tilt, Wobble, and Warp

• Image from NOAA
  
  Causes of global warming and climate change can be explained by Earth's rotation and revolution. Earth's tilt determines the angle of incoming solar radiation. According to the National Oceanic and Atmospheric Administration, Earth tilts on its axis on average at 23.5 degrees and varies from 22 to 24.5 degrees. This changes the amount of heat the surface is retaining, contributing to climate change. Revolving around the sun in an elliptical orbit puts the planet closer to the star in our Northern Hemisphere winter. A 100,000-year cycle of a warping orbit means this elliptical orbit becomes more circular at times. Wobbling along this revolution, according to the University of Montana website, causes 23,000-year fluctuations from the Northern Hemisphere experiencing summer when it is furthest from the sun to vice versa. Global warming could take place when the Northern Hemisphere is closer to the sun in summer.
  
  

Sunspots

• Increasing the number of sunspots, which are cool regions on the sun's surface, would seem to correlate with a cooling climate. According to the University of Wyoming Department Of Atmospheric Science, satellite data show increased irradiance coinciding with sunspots, making them a potential cause of global warming. The same website points out those sunspot minimums coincide with the colder periods of the Little Ice Age. Sunspots exhibit 11-year cycles and when these cycles are extreme, they cause global warming. Differing opinions emerge among scientists when discussing just how much sunspots contribute to the cause of global warming.
  
  

Greenhouse Gases and Urban Heat Islands

• According to the International Panel on Climate Change 2007 report, "most" of global warming is "very likely" due to anthropogenic greenhouse gas emissions. Carbon dioxide levels are about 365 parts per billion. Comparing this to Vostok ice core data, we see it's the highest level in 400,000 years. Core data show a positive correlation between increased greenhouse gases and temperature. The urban heat island effect, which is warming caused by decreasing albedo rates from increased urban sprawl, can't be counted out as a cause of global warming. This effect is accounted for in global climate models. However, the December 2007 research by Ross R. McKitrick questions the statistical accounting of the urban heat island effect. Combining these factors, the complexity of the cause of global warming is apparent.