Here is a link to a graph of Earth temps for the past 2000 years...by what ever means were available.
http://www.worldclimatereport.com/index.php/2008/02/11/a-2000-year-global-temperature-record/Note that there was a high point well above our current point around 1000. Also note there is a low point around 1800...which is known as The Little Ice Age. The temperature has been generally rising since that point.
Also note that Al Gore's chart started at that low point and the following rise is used to demonstrate the Global Warming Crisis and ignoring the preceding part of the graph that disproves human activity as a cause of global temperature change.
Not shown is the graph of where the GW proponents show the Earth's temperature to be in 400 years, the projected peak of Global Warming. That peak is just a bit below the peak around year 1000.
Either the Earth's temps are running at a natural cycle or the folks in 1000 BC had a completely undetected high carbon producing industrial base but managed to get it under control and reverse it's effects.
Also note that the counterparts of the GW crowd were warning of impending doom from cataclysmic drops in the Earth's temps in the 1960's.
The temps may be rising, but very little can be attributed to human activity. If this is so, we need to not be spending massive resources to curb human activity, which will only change the 400 year peak projection by a small fraction, but rather on adapting to the natural fluctuation of the Earth's temp. Build dikes, put houses on stilts or whatever works in an area, but don't waste those resources on buying carbon footprint reduction measures from an industry in which Al Gore is heavily invested.