You can look at the heat map scale on the bottom right, just remember that it's a bit misleading because the heat map only covers the range when data was availa

You can look at the heat map scale on the bottom right, just remember that it's a bit misleading because the heat map only covers the range when data was available (2002 through 2014 for CO2 concentration, but late 1800s to 2014 for surface temperature). Usually when we developers look at heat maps it ranges from an absolute zero (like number of clicks on a Web page) to a local maximum, but here "zero" is really a global average that is much higher than absolute zero temperature as defined in physics. The reality that these graphics represent is absolutely dire, but the way they are presented here isn't exactly the most honest representation of the data. For example, if we had CO2 concentration data for the last two thousand years, this graph would be much more informative because we'd go from grey to yellow over the time period 1700-1900 and yellow to red in the last century, which is much more representative of the changes in human CO2 production.