Since about 1979, each day satellites measure the temperature over about 80% of the globe to an accuracy of about 0.1 degree C. Weather balloons only make measurements at specific locations that are concentrated mostly over land (1).
The real signature of greenhouse warming is not surface temperature but temperature in the middle of the troposphere, about 5 kilometers up. If global warming is occurring from an increasing greenhouse effect due to CO2 additions by humans the temperature of the middle troposphere should be warming faster than Earth's surface (2,3). However, the opposite has been happening-- which suggests either the surface temperature records are in error or natural factors, such as changes in solar activity, may be responsible for the slight rise in surface temperatures (approximately 0.6° C, globally) that appears to have occurred over the past century.
Interestingly, in the 5 years leading up to 2007 the temperature of the mid troposphere has actually decreased slightly and surface temperatures have ceased warming-- even as CO2 concentrations have continued to increase (4). This should not be happening if CO2 increases to the atmosphere are the primary driver of global warming.
|Surface -vs- Satellite Temps|