Figure 4. World population growth. The global population has skyrocketed since the 19th century, jumping from about one billion in 1800 to 8.1 billion in 2024. UN officials estimate the global population will peak at 10.3 billion in 2080 and then begin to decrease. Source: Max Roser and Hannah Ritchie (2023), “How has world population growth changed over time?” Published online at OurWorldinData.org. Retrieved from: https://ourworldindata.org/population-growth-over-time, accessed 02 Sept 2025.
Failure to reach a plastics reduction agreement. Plastic pollution is an inherent part of the climate change crisis. Ninety percent of plastics are made in petrochemical plants, and plastic production is responsible for 3.3 percent of greenhouse gas emissions (2022 data), about the same as the commercial shipping industry. Global plastic production rose nearly 230-fold between 1950 and 2019, to more than 460 million tons a year. The current carbon footprint of plastics each year is equivalent to the emissions produced by 19-65 million cars annually. If no restraints or regulations are put in place, plastics production is expected to double by 2050 and triple by 2100, with an equivalent increase in emissions. Only 9% is recycled, according to the United Nations Environment Programme (UNEP). Single-use plastic – straws, containers, utensils, cups – make up 40 percent of the waste. An international effort to find a solution to plastic pollution, called the Global Plastics Treaty, was held in Busan, South Korea, in November 2024, but failed to reach a deal that would reduce plastic contamination. Environmentalists considered the plastics treaty as important as the 2015 Paris Agreement on climate change. Treaty advocates vowed to try again. A follow-on conference was held on August 5-14, 2025, in Geneva, Switzerland. However, as in South Korea, the conference participants failed to reach an agreement, blocked mostly by large petro-states such as Saudi Arabia, Russia, and the United States.
Sources: Paul Stegmann, et al, “Plastics Futures and their CO2 Emissions,” Nature, Vol 612, 08 Dec 2022; Hiroko Tabuchi, The White House has a Plan to slash plastic use in the U.S.,” New York Times, 19 July 2024; Boyan Slat, “Reducing Plastic Pollution in Our Oceans Is Simpler Than You Think,” New York Times, 25 May 2023; Lisa Anne Hamilton and Steven Feit, “Plastic & Climate: The Hidden Costs of a Plastic Planet,” Center for International Environmental Law (CIEL), May 2019; Andrew Jeong, “Divided over whether to stop making plastic, U.N. treaty talks collapse,” Washington Post, 01 Dec 2024; See the homepage of the Intergovernmental Negotiating Committee on Plastic Pollution. Link: https://www.unep.org/inc-plastic-pollution/session-5#:~:text=The%20fifth%20session%20of%20the,Center%20in%20Busan%2C%20Republic%20of accessed 01 Aug 2025.
The Ugly
Temperature increases are accelerating. About 50 percent of all the GHG emissions have entered the atmosphere since the establishment of the IPCC in 1988, one-third of them since 2005. Scientists refer to the rapid changes since 1950 as “The Great Acceleration.” The 2024 global jump in heat – the highest temperatures in human history - greatly exceeded the climate models, bewildering scientists and worrying many observers. In October 2022, in its latest assessment report, the IPCC warned that the planet was on track to cross the dangerous red line of 1.5 degrees Celsius by 2030. However, record-breaking conditions in 2023 and 2024 – temperatures that shattered scientific predictions – have shocked scientists and may breach the 1.5-degree Celsius threshold as early as 2027. Other indicators, such as global sea level rise and ocean temperatures, are also increasing at rates higher than predicted. The rapidly worsening conditions have caught some scientists off guard, and a large consortium of climatologists has warned that "the climate crisis has arrived and is accelerating faster than most scientists expected." Bottom line: we may have less time than we anticipated to get the climate crisis under control.
Sources: More than 11,000 scientists from 153 countries contended that the planet is facing a climate emergency. William Ripple, “World Scientists’ Warning of a Climate Emergency,” BioScience, vol 70, no. 1, January 2020; William Ripple et al, "The 2023 state of the climate report: Entering Unchartered Territory," BioScience, vol 30, no 0, 2023; International Energy Agency (IEA), “CO2 Emissions in 2022,” March 2023; World Meteorological Organization (WMO), 17 May 2023. The term “Great Acceleration” was first introduced at the 2005 Dahlem Conference on the history of the human-environment relationship. Will Steffen, et al, “The Trajectory of the Anthropocene: The Great Acceleration,” The Anthropocene Review, 2015; Will Steffen, Paul Crutzen, and John McNeill, “The Anthropocene: Are humans now overwhelming the great forces of nature?” Ambio, vol 36, no 8, December 2007; Global Carbon Project, ‘Data supplement to the global carbon budget 2021’, 2021, https://doi.org/10.18160/gcp-2021;
The Biodiversity crisis. According to the World Wildlife Fund, animal populations around the planet decreased by 73 percent from 1970 to 2020. One-third of fish stocks are overexploited. The number of natural ecosystems has declined by almost 50 percent. An estimated one million animal and plant species (out of about eight million) are at risk of extinction. According to the IPCC, 70–90 percent of the coral reefs will sustain irreparable harm at 1.5 degrees Celsius of global warming. If temperatures reach 2.0 degrees Celsius, an estimated 99 percent will be destroyed, eliminating an essential marine ecosystem that will have compounding effects on other ocean life and on humans.
Sources: The WWF and Zoological Society of London (ZSL) manage the annual Living Planet Index as an annual assessment of the ecological health of the biosphere. Link: https://www.livingplanetindex.org/, accessed 20 Jun 2025. The group’s methodology has been scrutinized closely. See, for example, Catrin Einhorn, “Here’s what a shocking new number on wildlife declines really means,” New York Times, 09 Oct 2024; James Ashworth, “Extinction threatens nearly a quarter of all freshwater species,” Phys.org, 18 Jan 2025; Francois Keck, et al., “The global impact on biodiversity,” Nature, 26 March 2025; IPCC, 2023: Sections. In: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II, and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, section 3.1.2, p. 71.
Donald Trump's scorched-earth campaign. The Trump Administration has devastated the climate change mitigation efforts of the United States. Historically, the United States has been the largest GHG emitter over time, although it was surpassed by China in 2006. The country has pumped more dangerous contaminants into the atmosphere than any other country. Moreover, the U.S. has the largest economy in the world, and five of the 50 U.S. states have economies that rank among the top 20 countries in the world. Contrary to all scientific evidence and without any evidence to back up his unfounded rhetoric, Trump called climate change a hoax and, in front of the UN General Assembly, declared, "All of these predictions made by the United Nations and many others... were wrong. They were made by stupid people who have cost their countries fortunes and given those same countries no chance for success.” The list of the administration’s efforts to undermine climate change is long. The United States is the only country in the world to have left the Paris Climate Accord. The Administration cancelled the congressionally-mandated National Climate Assessment, fired most of its scientists, and shut down all the webpages with information on the program. Top U.S. scientists were forced to cease work with the IPCC. Administration officials terminated more than two dozen carbon capture projects worth $3.7 billion. During the presidential campaign, he publicly asked for $1 billion in campaign funds from petroleum companies. He relaxed mileage standards for cars and trucks and cancelled tax breaks for purchases of electric vehicles. His administration has tried to cancel the EPA's endangerment clause, which declared GHGs as harmful to public health. Polluting companies no longer have to report emissions data to the EPA. His hand-picked scientists have attacked the validity of climate change in a bogus report. And he has ordered shuttered coal plants to reopen. The Trump administration’s shameful abandonment of its obligation to correct decades of GHG emissions is a major setback at a critical juncture of the decisive decade, one that may seal the fate of humanity.
Sources: Alexandra Witze, "Trump gutted two landmark environmental reports — can researchers save them?" Nature, 02 May 2025; Zachary Wolf, “The US Government has declared war on the very idea of climate change,” CNN, 01 Aug 2025; Lisa Friedman, “Energy secretary attacks offshore wind and dismisses climate change,” New York Times, 05 Sept 2025; Willam Broad, “Historian see autocratic playbook in Trump’s attacks on science,” New York Times, 31 Aug 2025; Maxine Joselow, “EPA to stop collecting emissions data from polluters,” New York Times, 12 Sept 2025; Lisa Friedman, “Scientists denounce Trump Administraiton’s climate report,” New York Times, 02 Sept 2025.
Tipping Points may have already being triggered. Some tipping points (often called "tipping elements" by scientists) may be triggered at temperatures between 1.5 and 2.0 degrees Celsius, the temperature recently reached in 2024. Because the 1.5 degrees Celsius threshold has already been crossed (in 2024), some feedback loops may already have commenced. These include the Greenland ice sheet, the West Antarctic ice field, coral reefs, and boreal permafrost. Others will be triggered at 3.0 degrees Celsius or higher. The IPCC's Sixth Assessment Report confirmed the same findings; the six tipping points at most risk of collapse were the West Antarctic Ice Sheet, the Greenland Ice Sheet, Arctic sea ice, permafrost, the Atlantic Meridional Overturning Circulation (AMOC), and the Amazon rainforest. Scientists warn that a runaway greenhouse gas effect could raise planetary temperatures to a "hothouse Earth" situation, which would make life unsustainable on the planet. In sum, the takeaway from this section is twofold: first, humanity may not have much time as it believes to take aggressive action to reduce GHG emissions, and second, the consequences of inaction may be much more consequential than many believe.
Sources: David Armstrong et al, "Exceeding 1.5 degrees Celsius global warming could trigger multiple climate tipping points," Science, 377, 09 Sept 2022; Will Steffen et al, "Trajectories of the Earth System in the Anthropocene," Proceedings of the National Academy of Sciences (PNAS), vol 115, no. 33, 14 August 2018; Timothy Lenton et al, "Climate tipping points – too risky to bet against," Nature, vol 575, 28 Nov 2019. Also reported by Johan Rockstrom, “Tipping Points and Feedback Loops,” p. 37, in Greta Thunberg’s The Climate Book. Timothy Lenton, et al, "Climate tipping points – too risky to bet against," Nature, vol 575, 28 Nov 2019.
