Urgent reduction in greenhouse gas emissions is needed to avoid irreversible tipping points: Time is running out

Abstract

ABSTRACT This 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.