About climate graphs ….
I want to draw your attention to something else about this graphic that is important to the understanding of our current situation. Reading graphs is somewhat of an art, and a course or two in Statistics is standard fare for undergraduate training of all scientists. If you haven’t had the training then you may be missing a few important points because it is very easy to make charts that are misleading. And this is how we are being misled. Careful manipulation of either of the two axis, the vertical temperature range or the horizontal time period can support any claim, either way. You simply have to be a discerning viewer each and every time.
Secondly, any discussion of human survivability needs to take into consideration that we flourish very nicely between -50C and +50C. True, +20C is our comfort zone and whenever we are able to control our environment we dial it into something close to +20C. But you have to be skeptical about any graph that dials it down to fractions of one degree and base their whole claim on a squiggly line going up or down over such a small temperature range.
Manipulation of the time axis is just as insidious. Notice for example, in the above graph that the temperature is constantly changing, from one century, or millenium, to the next. It can be seen to move very rapidly for periods of time and frequently it can be seen to move in the opposite direction of the long term trend-line for a period of time. You need to notice that these periods where the temperature is bucking the trend can be quite long and have relatively large ranges. For example look at the period 66 thousand years ago up to about 58 thousand years ago and notice that the temperature increased steady from about -9 to about -5. This is a whopping 4 degrees C INCREASE over a period of 8 thousand years even though the long term trend was DOWNWARD. If you were able to graph only the time period 66 thousand years – 58 thousand years, you would have everyone believing the opposite of what was actually happening.
Lastly you have to be skeptical about an claims that are made about the future. When you pass from observed data into projected data, you are passing from reality into fiction.