Satellites are much more reliable in measuring temperatures than thermometers, because they can cover large areas, while thermometers are located in few areas and are much influenced by their environment. Then maintenance of land based weather stations is a mess.

Thermometer measurements would be a scientific fraud for the study of climate even if they were totally accurate. First, they do not exist over the 70% of the earth covered by oceans. Then there are very few in the impoverished countries. So something like 10% of the earth's surface is actually measured. Then localized effects are highly variable for unknown reasons. Why was there a severe drought in the US state of Georgia for several years while nearby states were flooding? No one knows. Much of the variation is obvious due to changing environments which human activity creates.

A few years ago, satellite measurements were showing no significant increase in global temperatures, while thermometers showed a small increase. So satellite data was adjusted to conform to thermometer measurements.

One of the explanations given for altering the satellite measurements was that near-earth satellites gradually slow down over time due to thin atmosphere which they pass through. Slowing down would move them closer to the earth and create a higher read. So the satellite data would have needed to be lowered; but it was increased. The adjustment was in the opposite direction of the explanation. The frauds obviously did no analysis of satellite motion; they just faked the data and lied about it.

The net result of the fake temperature measurements was to show a 0.6°C average, global temperature increase over the past 150 years, of which 0.2°C was attributed to the primary effect by CO2 and 0.4°C was attributed to a multiplier effect from water vapor. Notice that the claimed 0.2°C effect by CO2 over 150 years is equal to 0.0013°C per year or 0.00011°C per month. Such miniscule "climate change" could not cause anything noticeable to happen on a yearly or monthly basis.

Fake Science

The manipulation of numbers is discussed by Patrick Michaels here:
Our Climate Numbers Are a Big Old Mess
The Wall Street Journal. April 18, 2008

Hansen's standard of manipulating numbers is discussed here:
Dissing Hansen - by Peter Glover

More on Hansen's manipulation of numbers:
Is the earth getting warmer, or cooler? A tale of two thermometers
Steven Goddard, The Register, May 2, 2008

The mess of weather stations is discussed by Anthony Watts here:
Where Thermometers Go To Die - How Not to Measure Temperature

John Christy compares land based measurements with satellite data:
What if global-warming fears are overblown?

Patrich Michaels describes how the thermometer data disappeared:
The Dog Ate Global Warming
September 23, 2009