On November 22, 2025, Scientific American reflected on the ten-year milestone of the 2015 Paris Agreement, a landmark global treaty aimed at combating the escalating climate crisis. The Paris Agreement set ambitious goals for the world to keep global temperature rise “well below” 2 degrees Celsius above preindustrial levels, while striving to limit warming to 1.5 degrees Celsius. These targets were designed to prevent the most catastrophic impacts of climate change, requiring nations to begin reducing greenhouse gas emissions significantly by 2025. As the world marks a decade since this historic accord, the reality is complex: meaningful progress has been made, but formidable challenges remain.
The Paris Agreement was born out of a collective recognition that climate change poses an urgent threat to the planet. Its core mission is to limit global warming, measured against temperatures recorded during the late 19th century, often regarded as the preindustrial baseline. Since 1970, global average temperatures have consistently risen above this baseline, and the trend shows no signs of slowing. When the agreement was signed in 2015, the world was already experiencing a 1.1 degrees Celsius increase in average temperature compared to preindustrial times. Today, that figure has climbed to approximately 1.3 degrees Celsius. Notably, 2024 marked the hottest year on record, with temperatures exceeding 1.5 degrees Celsius above the preindustrial average. The World Meteorological Organization projects that 2025 will be among the second or third hottest years recorded, with global temperatures about 1.4 degrees Celsius above that baseline.
While these numbers are alarming, they do not represent the end of the story. Experts emphasize that every fraction of a degree avoided matters immensely. Costa Samaras, an energy policy specialist at Carnegie Mellon University, stresses that “every ton” of emissions reduced, every tenth of a degree of warming prevented, and every year of delayed warming can significantly influence future climate outcomes. The key lies in rapidly curbing greenhouse gas emissions to reverse the upward trajectory of global temperatures.
Prior to the Paris Agreement, climate models predicted a grim future with global temperatures rising between 3.7 and 4.8 degrees Celsius by the end of this century. However, if countries implement their Paris commitments effectively, these projections improve somewhat, with warming expected to reach around 2.9 degrees Celsius — still a dangerous rise, but notably less severe. Estimates suggest a likely range of 2.3 to 3.4 degrees Celsius increase, reflecting the complexity and uncertainty inherent in climate modeling. Despite this progress, Samaras cautions that as long as global emissions remain above net zero, climate impacts will worsen over time. Achieving net-zero emissions is thus critical to halting the progression of climate change.
The consequences of failing to meet these goals are stark. New research illustrates the dramatic increase in extreme heat events that could occur under various warming scenarios. For example, by the end of this century, if global temperatures rise by about four degrees Celsius, U.S. residents could face 118 more days of extreme heat annually compared to preindustrial times. Such extreme heat days bring severe health risks, strain infrastructure, and disrupt ecosystems. If the current emission reduction pledges are fulfilled, this number could fall to 88 days per year — still a significant increase but a notable improvement. Limiting warming to 1.3 degrees Celsius, close to today’s levels, would reduce these extreme heat days to around 58 annually, emphasizing the tangible benefits of stronger climate action.
Yet, even if the Paris goals are met, climate change will continue to impact society unevenly across generations. Studies led by climate scientist Wim Thiery at Vrije University of Brussels reveal a stark intergenerational disparity in exposure to climate extremes. Children born today and those currently under ten will endure significantly more heat waves throughout their lifetimes than previous generations. For instance, today’s five-year-olds are projected to experience 22 percent more heat waves than fifteen-year-olds do now. Moreover, today’s children will face more than twice as many heat waves as their parents in their mid-thirties and over six times as many as their grandparents in their mid-sixties. This trend underscores the urgency of addressing climate change not only for current populations but for future generations as well. Climate-related disasters like droughts, wildfires, and stronger tropical cyclones are also increasing in frequency and severity, compounding the risks.
Despite these daunting challenges, there are noteworthy successes that offer hope