Summary: | ABSTRACTThis essay addresses climate change and its main causes over the last three decades. Between 1992–2021, global emissions of greenhouse gases (GHGs) have risen continually. Specifically, the major socioeconomic sectors – including (1) energy, (2) industry, (3) land-use/land-use change/agriculture, (4) transportation, (5) building/construction, and (6) waste treatment/disposal – have emitted enormous amounts of GHGs. Between 1992–2019, the combined annual GHG emissions have risen by 53% – from 32.6 to 49.8 Gt CO2 equivalent (CO2e). The combined GHG concentration has increased by 33% – from 382 ppm CO2e in 1992 to 508 ppm CO2e in 2021. The combined radiative forcing has surged by 45% – from 2.226 W m−2 in 1992 to 3.222 W m−2 in 2021. At the current emission rate, the entire GHG credit for limiting global warming to 1.5°C or 2.0°C – according to the Shared Socio-Economic Pathway (SSP) 1–1.9 or SSP1–2.6, respectively – in 2100 compared to preindustrial levels may be fully exploited by~2030. Limiting global warming to 1.5°C or 2.0°C will require total GHG emissions to peak before 2025 at the latest, and be reduced by 43% or 25%, respectively, in 2030 relative to 2019, followed by zero net emissions in the early 2050s or 2070s, respectively.
|