Month: July 2016

THREE MAPS ILLUSTRATING SIMILAR GLOBAL SURFACE TEMPERATURE CHANGES OVER DIFFERENT 30-YEAR PERIODS

The GISS map-making webpage allows users to create global maps of surface temperature anomalies for specific time periods or to create maps of the change in surface temperatures over user-defined time periods based on local linear trends.

My Figure 1 includes 3 maps from that webpage.  They are color-coded to show where and by how much surface temperatures have changed around the globe over three different 30-year periods, based on the GISS Land-Ocean Temperature Index (LOTI) data.  I’ve highlighted in red the respective global temperature changes in deg C.  They’re basically the same at 0.48 deg C and 0.49 deg C. You’ll note that I’ve also blacked-out the time periods, because I’ve asked the question Which 30-Year Warming Period Is Recent?

Figure 1

A guest post by Nic Lewis

Introduction and Summary

In a recently published paper (REA16),[1] Mark Richardson et al. claim that recent observation-based energy budget estimates of the Earth’s transient climate response (TCR) are biased substantially low, with the true value some 24% higher. This claim is based purely on simulations by CMIP5 climate models. As I shall show, observational evidence points to any bias actually being small. Moreover, the related claims made by Kyle Armour, in an accompanying “news & views” opinion piece,[2] fall apart upon examination.

The main claim in REA16 is that, in models, surface air-temperature warming over 1861-2009 is 24% greater than would be recorded by HadCRUT4 because it preferentially samples slower-warming regions and water warms less than air. About 15 percentage points of this excess result from masking to HadCRUT4v4 geographical coverage. The remaining 9 percentage points are due to HadCRUT4 blending air…