In starting a discussion on the dangers of Anthropological Global Warming (AGW), the first thing we must do is see where there’s agreement and where there’s disagreement. Often those who question the veracity of the dangers are seen as anti-science and this will help separate those who deny science from those who question the accuracy of the dangers of AGW. So in that vein, here are things to which everyone should agree:
- CO2 is a greenhouse gas. Yea, there is no doubt. There is no scientific discussion. As a greenhouse gas and absent any secondary effects (positive and negative), increasing the concentration of this gas should increase the temperature. Here is a plot of atmospheric CO2 concentrations taken from Mauna Loa:
- The worldwide temperature has been increasing since the Little Ice Age. This period is, according to Wikipedia, commonly accepted to have lasted from 1300 AD through 1850 AD. The causes of the LIA are not well understood and in this discussion, are going to be caused by the all-encompassing term “natural variability”. Since the thermometer had yet to be invented, we can only reconstruct the temperatures by indirect methods called proxies. Here’s a collection of estimates of worldwide temperature based on such proxies during this time frame (we will be discussing the accuracy of these proxies in an upcoming post):
- As stated above, modern temperatures are rising. Here’s a plot of the temperatures since the thermometer record began (around 1880):
- Sea levels are rising. Accurate measurements of sea level rise is difficult as tidal gauges are the most common and longest records but often they do not account for land subsidence (the lowering of the land). Satellite measurements are more accurate, but the record is short and no useful in determining changes in trends. The average rise in sea level for the last 150 years is between 2 and 3 mm/year and is almost perfectly linear. Here’s a plot of sea level rise taken from Wiki:
- The final assumption is that all future predictions are based upon climate models. This should be obvious, but it needs to be stated that these are just predictions based upon models. As such, these models must be shown to be accurate (verified) before the results can be trusted. Here is what the IPCC showed as the potential future temperatures based upon these models (2007):
These are the big assumptions. In future posts I will be going into these areas (and others) more in depth and will include links to all the files I use.