Over the weekend in response to Better Century promotions we’ve put out there have been a series of climate deniers writing back mainly by facebook. I personally want to ensure everyone has the information to hand so they can make their own mind up about climate change. It would be great if others could add what arguments they encounter, so we can make this a go to source of information on this matter. We also welcome climate deniers to contribute to this discussion!
The Basis of Climate Science
The climate has changed mainly due to Milankovitch cycles, determined by the tilt of the earth and the way we move around the sun. Geologists challenge Milanokitch’s mathematical equation for the temperature of the earth as after warming periods going back 100s of millions of years ago the temperature didn’t come back down for thousands of years. They finally agreed that this caused this was the green house effect. And also agreed that a higher concentration carbon dioxide in our atmosphere results in more solar energy being absorbed, resulting in higher temperatures and more erratic weather.
Natural climate fluctuations do occur from our movement around the sun but the maximimums and minimums of these fluctuations occur over 100,000 years. Sun Spots and Volcanic Activity result in changes to global temperatures. Sun spots cause the sun to release a flare from interactions with our magnetic field and cause temporary heating. Volcanic activity as result in the release of aerosols increasing temperature or volcanic dust blocking the suns light and decreasing temperature.
Literature reviews show that 97% percent or more of actively publishing climate scientists agree*: Climate-warming trends over the past century are extremely likely due to human activities. The International Panel on Climate Change (IPCC), which pulls climate scientists across the world, have produced reports to that affect dating back to 1990. Global temperatures rose 0.87 degrees from 2006 - 2015 and will increase to 1.5 degrees at some point between 2025 and 2040, where it is likely that humans may not be able to stop further global warming.
Medieval Warming Period Climate Denial Argument
The Medieval Warm Period (MWP) also known as the Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region lasting from c. 950 to c. 1250. This warming period is an anomaly in climate science and often pointed to as a flaw in current climate thinking.
Many studies show that the amount of warming occurring during the MWP varied by season and region. Some provide evidence of relatively warm temperatures (most pronounced during the summer months) in several regions, including the North Atlantic, northern Europe, China, and parts of North America, as well as the Andes, Tasmania, and New Zealand. Other studies maintain that the temperature conditions of certain regions, such as the Mediterranean, South America, and other locations in the Southern Hemisphere, were essentially no different from those of the present day.
Many scientists arguing for the existence of the MWP have noted that the interval was characterized by an increase in incoming solar radiation paired with a relative absence of volcanic activity. (Aerosols expelled from volcanic eruptions have been shown to block a portion of incoming sunlight.) The combination of both phenomena would contribute to an increase in air temperatures. Some scientists have also attributed warmer air temperatures in the North Atlantic region to the delivery of warmer seawater (heated by solar radiation unimpeded by volcanic aerosols) by the Gulf Stream and other currents.
The counter argument
The medieval warming period was not caused by Milankovitch cycles or concentration of CO2 in the atmosphere. What we are seeing today isn’t being caused by the same factors, and the impacts are much longer lasting. We know that if the concentration of CO2 in our atmosphere remains at this level we will continue to warm, and unless we stop producing CO2 then the affect will become worse.