To: Wharf Rat who wrote (61760 ) 12/8/2014 12:26:52 PM From: Wharf Rat Read Replies (1) | Respond to The most popular deceptive climate graphThe “World Climate Widget” from Tony Watts’ blog is probably the most popular deceptive image among climate “skeptics”. We’ll take it under the microscope and show what it would look like when done properly. two other examples deconstructed at Realclimate). The image below is especially widespread. It is displayed on many “climate skeptic” websites and is regularly updated.The “World Climate Widget” of US “climate skeptic” Anthony Watts with our explanations added. The original can be found on Watts’ blog What would a more honest display of temperature, CO2 and sunspots look like? It is better to plot the surface air temperature . That is what is relevant for us humans: we do not live up in the troposphere, nor do natural ecosystems, nor do we grow our food up there. By the way, the satellite-based tropospheric temperatures shown by Watts show almost the same climatic warming trend as those measured by weather stations near ground level ( in both cases 0.16 C per decade over the last 30 years ). However, variability in the tropospheric data is considerably larger, especially because of higher sensitivity to El Niño (as happened in 1998) and the solar cycle (we showed that in Foster and Rahmstorf ERL 2011 – when corrected for those factors the surface and troposphere data agree closely ). Because of increased noise, the trend is less obvious to the eye, especially if one shows monthly values which adds yet more noise. Let us thus use the GISTEMP global annual temperature record from NASA’s Goddard Institute for Space Science (all surface data sets agree to better than 0.1 °C, see comparison graph ). One needs to scale the CO 2 data correctly for an honest comparison with temperature, so that it can actually be used to evaluate climate scientists’ predictions of the CO2 effect. You can calculate this with a complicated climate model, but one can also use a back-of-envelope estimate. A CO2 increase from 280 to 400 ppm (equivalent to 2 Watts/meter2 radiative forcing) produces about 1 °C of global warming (at the time when 400 ppm is reached – some further warming will follow with delay). Thus, an increase of 100 ppm CO2 on the right hand side of the graph corresponds to a temperature increase of 0.8°C on the left hand side. That matches the IPCC’s estimate of the “transient climate response (TCR)” of ~2°C at the time of CO2 doubling (see Technical Summary of the IPCC WG1 report, p. 84). The TCR is smaller than the equilibrium climate sensitivity (about 3°C for doubled CO2) because it takes time to warm the oceans. The full equilibrium warming is thus only reached after a time delay. We are going to use the annual values from the famous CO2 measurements which began in 1958 on Mauna Loa in Hawaii. And last but not least one should show honest sunspot data (annual time series) , not just a snapshot of the number of spots on the sun today (which is completely uninformative for climate purposes – it’s apparently been added to the widget simply to insinuate an important role of the sun). Here also there is a question of the proper scaling (which is actually not that important because solar activity is cyclical and shows no significant trend over the period of the graph) . We will chose the scaling from the correlation analysis of Lean and Rind (2008) from which one can find a measurable effect on global temperature with an amplitude of 0.05°C. When done this way the graph looks like this:KlimaLounge , Bernd Herd, has programmed a widget for this graph so it can be added to any website at a size you like, automatically updated annually.Lean and Rind 2008 , Foster and Rahmstorf 2011 ). The IPCC AR5 found their contribution to global temperature change since 1951 to be in the range of -0.1°C to 0.1°C.Weblink A quick ‘n dirty guide to falsifying AGW realclimate.org
