The view

Where did IPCC 1990 Figure 7c Come From?

In a way, the use of this graphic by Crowley in 1996 and by Bradley and Eddy in 1991 is even more interesting than its use by IPCC in 1990. It shows that this schematic represented the view of the most senior people in the field as late as 1996, right up to the MBH hockey stick – in which Mann introduced the Graybill bristlecone chronologies – previously avoided in temperature reconstructions.

The left triptych image is from Crispin Tickell (British Antarctic Survey) compared to the corresponding triptych used until 1996 by the IPCC.


To say that the sun is no more than one suburban star in a galaxy of one hundred thousand million stars and that this galaxy is no more than one among a hundred thousand million galaxies is to speak in abstractions. But we can have a sense of distance in our own backyard. If the sun is reduced to the size of an orange, the earth is a grain of sand at thirty feet, and the nearest star – another orange – is a thousand miles away.

The scale of time is even harder to grasp. When in the last century a poet described the desert ruins of Petra as “rose-red city half as old as time”, he meant it literally. For him, absolute time began 4,000 years before Christ. For us, relative time began with the universe we can see, around 15,000 million years ago; and according to our calculations the earth was formed about 4,600 million years ago.

Suppose we knock off the zeros and reduce 4,600 million years to 46 years (a good life span in most human history), then the dinosaurs died just over 6 months ago, the present human breed emerged about a week ago, our counting system before and after Christ began less than a quarter of an hour ago, and the Industrial Revolution has lasted just over a minute.

More relevant to our present purposes, on the same time scale there were major ice ages on the earth nine and one-half years, seven and three-quarter years, six and one-quarter years, four and one-half years, and around three years ago. The most recent series of glaciations began less than a week ago, and the last glaciers retreated about an hour ago.

In this perspective, we live in a tiny, damp, curved space at a pleasantly warm moment.

Climate is constant only in its variability.

Crispin Tickell


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