In time series analysis picking the right time scale is everything.<p>Let´s do a small experiment:<p>One hot summer day I measure the temperatures in my home town between 6:00 and 12:00 and I get some data like this:<p>6:00 - 10 C<p>...<p>12:00 - 32 C<p>Now I make a small regression analysis and say that at 24:00 we are going to die a painfull death because the temperature will raise with a probability of 95% to 70-80 C.<p>In this case I obviously forgot about the periodicity of daily temperatures.<p>The global temperatures have a periodicity of ca. 400.000 years. Therefore any analysis based on a time period shorten than 400k years has the same problems as my summer experiment.<p>&gt;&gt; the end of the century our planet might be experiencing environmental conditions never previously encountered by our species<p>- 2*2 might be 5...<p>- at the end of the century I will be dead and &quot;our species&quot; will be only one of million other species. For example the dinosaurs loved the 12 C more and had a happy life on the ice-free antarktis a couple of million years ago...