Read the following passage carefully and answer the question given below

Climate change involves both internal and external factors. External one includes solar variability, astronomical effects on the earth's orbit and volcanic activity whereas internal one includes natural variability in the system, feedbacks within atmosphere, ocean and land surface. Recently. human-induced climate change on global and local scale has become a reality, primarily through changes in atmospheric composition and surface properties. Climate changes involve continental drift, volcanic activity and solar output. Glacial-interglacial cycles have been controlled by astronomical variations. The global temperature has increased by 0.5°C with greatest in the middle latitudes with warming particularly during the 1920 to 1940s and 1990s with several warmest years. Long-term changes are ascribed to astronomical forcings, while short-term changes linked to anthropogenic factors causing changes in atmospheric composition, including aerosol loading, depletion of ozone, destruction of vegetation etc. Recently, climate change predictions with GCMs are under taken for next 100 years depending on emission scenarios for green house gases and aerosols the mean global temperature may increase in the range of 1.4 to 5.8°C, together with sea level rise. To conclude, critical resarch data on cloud cover, radiation, ocean processes atmospheric coupling and feedback processes in the context of climate change are required.