1500BC, or maybe 5100BC?Â The CO2 levels 7000 years ago were a lot less than today. The point is that the temperature has been changing on earth for millions of years, and the real question is, is the current temperature increase within normal bounds or an outlier? This is the crux of the Climate Change debate. Take Greenland ice core data. These estimate the temperature based on the isotopes of oxygen found in the tiny bubbles of air trapped in the ice. Its a proxy, an estimate for past temperatures. If the ice core data is right then the warming of the part 100 yearsÂ is just part of the normal climatic movement. We had the Medieval Warm period, followed by the Little Ice Age, that now we are warming up to get back to temperatures that have occurred in the past.
All the discussion in the media with temperature graphs and comparisons focuses on the last 60-100 years. If it was as warm, or even just close to as warm 2000 years ago during the Roman Warm Period with no increased CO2 levels, then how did that happen?Â If the British were harvesting grapes in the Medieval Warm period, with no extra CO2 levels, then how did the temperature increase then?Â If 2010 is the hottest year in the last hundred years, or the last ten years, does it really matter if it was even warmer 2000 years ago?