Natural climate change is cyclic on many time scales, so long-term straight line trends are misleading. There has been no atmospheric warming since 1998.
The graph above shows the temperature changes of the lower troposphere from the surface up to about 8 km as determined from the average of two analyses of satellite data. The UAH analysis is from the University of Alabama in Huntsville and the RSS analysis is from Remote Sensing Systems. The two analyses use different methods to adjust for factors such as orbital decay and inter-satellite difference. The best fit line from January 2002 indicates no trend. Surface temperature data is contaminated by the effects of urban development. The Sun's activity, which was increasing through most of the 20th century, has recently become quiet, causing a change of trend. The magnetic flux from the Sun reached a peak in 1991. The high magnetic flux reduces cloud cover and causes warming. Since then the Sun has become quiet, however it continues to cause warming for about a decade after its peak intensity due to the huge heat capacity of the oceans. So we expect the warming to peak at about 2002. The green line shows the CO2 concentration in the atmosphere, as measured at Mauna Loa, Hawaii. The ripple effect in the CO2 curve is due to the seasonal changes in biomass. There is a far greater land area in the northern hemisphere than the south that is affected by seasons. During the Northern hemisphere summer there is a large uptake of CO2 from plants growing causing a drop in the atmospheric CO2 concentration.
Cool periods in 1984 and 1992 were caused by the El Chichon and Pinatubo volcanic eruptions. The temperature spikes in 1998 and 2010 were cause by strong El Ninos.
Natural climate change is much stronger than any effect from carbon dioxide.
A surface temperature index is produced by the U.K. Met Office. The graph below shows the best fit trend from January 2002. It shows a cooling trend. The graph also shows the average IPCC climate model projection during the period.
The graph below shows there has been no warming for 16 year 3 months to July 2013 by the best fit linear line.
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