Final answer:
The claim that IPCC AR4 carbon emissions have minimal impact on projected global temperatures is false. Carbon emissions have a significant effect on global temperatures and their spatial distribution, with various scenarios predicting substantial increases in temperature, especially over land and in the Arctic.
Step-by-step explanation:
The statement that IPCC AR4 carbon emissions have little impact on the magnitude and spatial patterns of projected global temperatures over the next two decades is false. According to the IPCC Special Report on Emissions Scenarios, there are varying levels of emissions scenarios, including low (B1), medium-high (A1B), and high (A2) emissions scenarios, which all suggest differing levels of rise in global temperatures relative to the 1961-1990 averages. These scenarios clearly indicate that carbon emissions will significantly affect both the magnitude and distribution of global warming.
Climate change is driven by the accumulation of CO₂ in the atmosphere from the burning of fossil fuels, with models predicting a potential increase in mean global surface temperature of 0.3-4.8 degrees C (0.5-8.6 degrees F). Furthermore, the effects of warming are expected to be greater on land and particularly profound in the Arctic region. The core physics of the climate response to rising CO₂ levels is well-established, linking CO₂ rise to temperature consequences.
Additionally, the concept of a 'global warming hiatus' is identified as a form of cherry-picking data which neglects the longer-term warming trends (red trend lines). The IPCC reports and scientific studies, including those by Solomon et al. (2009) and Thomas et al. (2004), emphasize that future carbon emissions will have major consequences for global temperatures and the planet's life-support systems, with more complex and harder to manage impacts on biological diversity.