Indirect estimates of temperature change from such sources as tree rings and ice cores help to place recent temperature changes in the context of the past.
From this analysis, they estimated, with 93 percent certainty, that somewhere between 17 and 35 percent of Americans are atheists, with a «most
credible indirect estimate» of 26 percent.
In terms of the average surface temperature of Earth,
these indirect estimates show that 1983 to 2012 was probably the warmest 30 - year period in more than 800 years.