Final answer:
The IPCC AR4 projection indicates that temperature increases by 2100 will be greater over land than over water, with the Arctic experiencing particularly significant warming. Ground-level air temperatures will continue to warm more rapidly on land, and despite reductions in emissions, warming will persist due to existing greenhouse gases.
Step-by-step explanation:
The IPCC AR4 multi-model climate projection suggests that by the year 2100, temperatures will increase more significantly over land compared to over water.
This is primarily because land has a lower capacity to absorb heat compared to water. Additionally, the Arctic region is projected to experience the greatest warming, although the exact reasons for this are not fully understood. Multiple factors contribute to this disparity in warming, including the different heat absorption capacities of land and water, and specific regional climatic changes.
Ground-level air temperatures are anticipated to warm more rapidly over land than oceans, with the possibility of temperature increases ranging broadly depending on future greenhouse gas emissions. It is expected that global average temperatures could warm at least twice as much as they have in the last 100 years. Regardless of the reductions in greenhouse gas emissions, the warming trend is set to continue due to existing atmospheric greenhouse gases.
Furthermore, patterns of temperature and rainfall are shifting globally, with increases in both average temperatures and the frequency and intensity of extreme weather events like heatwaves. These changes will likely have profound impacts on various ecosystems, prompting shifts in species distributions and other systemic changes.