Pengaruh Ketidakpastian Eksternal (Perubahan Iklim, Ketidakstabilan Politik, serta Pandemi COVID-19) terhadap Kinerja Keberlanjutan Perusahaan di Negara G20 Tahun 2011-2020 = The Effect of External Uncertainty (Climate Change, Political Instability, Economic Policy Uncertainty, and the COVID-19 Pandemic) on Company Sustainability Performance in the G20 Countries in 2011-2020