(Part of the How to Talk to a Climate Skeptic guide)

Objection: Despite what the computer models tell us, there is actually no evidence of significant global warming.

Answer: Global warming is not an output of computer models; it is a conclusion based on observations of a great many global indicators. By far the most straightforward evidence is the actual surface temperature record. While there are places — in England, for example — that have records going back several centuries, the two major global temperature analyses can only go back around 150 years due to their requirements for both quantity and distribution of temperature recording stations.

These are the two most reputable globally and seasonally averaged temperature trend analyses:

Both trends are definitely and significantly up. In addition to direct measurements of surface temperature, there are many other measurements and indicators that support the general direction and magnitude of the change the earth is currently undergoing. The following diverse empirical observations lead to the same unequivocal conclusion that the earth is warming:

There is simply no room for doubt: the Earth is undergoing a rapid and large warming trend.