As of July 2015, no similar study has been conducted on a global basis. * From 1979–2014, the three temperate datasets posted above differed from one another by an annual average of 0.13ºF (0.07ºC).The largest gap between any of the datasets in any year was 0.38ºF (0.21ºC), and the smallest gap was 0ºF/C: * To reconstruct global average temperatures in the era before instrumental measurements were made on a global scale, scientists use proxies that respond to changes in climate, such as the widths of tree rings and certain elements of the geological record, to estimate temperature variations in the past.  * The Intergovernmental Panel on Climate Change (IPCC) is a scientific body established in 1988 by the United Nations and World Meteorological Organization.The report states that: some of the global warming since 1850 could be a recovery from the Little Ice Age rather than a direct result of human activities.
Hopefully it will give some insight into the science and the people behind it.  Look at the instrumental record!
There are huge differences between different regions - Alaska has warmed substantially while eastern North America cooled after the 1950s.
For instance, the sea level in the Indian Ocean is about 330 feet below the worldwide average, while the sea level in Ireland is about 200 feet above average.
Such variations are caused by gravity, winds, and currents; and the practical effects of these phenomena are dynamic.
A caveat of this finding is that it is based upon weather balloon data, which “must be treated with great caution, particularly at [higher] altitudes….”  states that the “sign and the magnitude of the global mean cloud feedback depends on so many factors that it remains very uncertain.” This is because some types of clouds trap heat while others reflect it.   found that ice clouds (also called cirrus clouds) exert a “strongly negative” feedback to temperature changes, regardless of whether these changes are increases or decreases.