NASA recently posted two videos on YouTube dealing with climate change. The first shows the statistical distribution of summer temperature anomalies for the Northern Hemisphere by decade from 1950 to 2001. The distribution is relatively stable for the decades whose centers range from 1955 to 1980 then the mean temperature of the distribution starts to increase. The temperature anomaly is difference between the measured temperature and a reference temperature. The trend has been one of an increasing anomaly over the last century. What happened about 1980 that might have caused the increase? The Three Mile Island accident occurred in 1979 and the number of nuclear reactors that have been licensed since then has fallen off. The anomaly was relatively constant over the period from the Forties to Seventies when they were constructing reactors. Could turning away from nuclear energy have caused global warming? We have had to rely more on fossil fuel plants which released CO2 into the atmosphere. But fossil fuel consumption shows a steady increase from 1950. The record for global biomass burning shows some correlation with the temperature anomaly but not during the last 50 years. Mt St Helens erupted in 1980 but there have been other large eruptions too. It is difficult to link cause with effect when there are so many possible contributing factors. We need to understand what is happening before we can choose the actions that will help remedy the situation.
Supplemental (Jan 19): The amount of ice in the world is a remnant of the last ice age and it has been slowly disappearing over the centuries. When the world loses heat during winter it has a choice of cooling ice or making more ice. The formation of ice acts as a floor for low temperatures and transports the cold to cool the summers. Water evaporating in summer also helps cool the land but less melting snow and ice leads to warmer and dryer summers. This may be what we are seeing in the temperature anomaly. One might make an analogy of a plane on a runway gaining speed. The faster it goes the more lift it gets but it needs to reach a certain speed before it takes off. This speed may be the tipping point that the environmentalists are like to refer to. We may be close to the turning point but don't have enough speed yet to get airborne. Some parts of the world are already airborne. They don't have snow at any time of the year. Other areas are grounded all year and there is no time that they are free of snow or ice. The world is in transition and has been for a long time now with the boundaries moving northward.