On the Emergence of Human IInfluence on Surface Air Temperature Changes Over India
Researchers from the Indian Institute of Technology Delhi, Lawrence Livermore National Laboratory, and India Meteorological Department analyzed climate model simulations and observational data to reveal that the observed warming over India from 1906 to 2005 is largely driven by the increase in greenhouse gases and partially offset by regional anthropogenic emissions of aerosols.
Past studies have shown that near-surface air temperature changes on a global scale are attributable to human activities. On regional scales, this is a point of consideration as the attribution of the causes of temperature change is vital for making informed adaptation and mitigation policies. This study reveals the patterns of change in near-surface air temperature from individual forcings and quantifies their contribution to observed changes.
Many studies have performed detection and attribution analyses of surface air temperature changes on a global scale. There has also been considerable (and increasing) evidence for an anthropogenic influence on other estimates of climate change at regional scales. Here we address the questions: What are the major external forces responsible for the increase in surface air temperature over India? Can we isolate the response to various external forcings at regional scales using model simulation experiments? We present the results of an investigation into the causes of changes in surface air temperature over the Indian region from 1906 to 2005 using a pattern-based fingerprint study. The model fingerprints of the temperature response to external forcings are detectable in observations with high statistical confidence. Our results indicate that internal variability alone cannot explain the observed changes in surface air temperature. We carried out the analysis with multiple observational data to explore the sensitivity of results to the choice of dataset. Signals are detected in both periods (1906-2005 and 1956-2005) in CRU but not in IMD for the 1956-2005 period. Therefore, the results are sensitive to the choice of observational dataset. Our findings with MME suggest that the rapid increase in the TAS trend is primarily due to human-induced increases in greenhouse gases and partially offset by anthropogenic aerosols and natural forcings.