20 Climate Facts
Given to us by distinguished Atmospheric Scientist and Lead Author for the IPCC Dr. Don Wuebbles
1. The current rate of climate change is over ten times faster than any global climate changes in the last 20,000 years.
2. Global, annually averaged, surface air temperature has increased by about 1.8°F (1.0°C) over the last 115 years (1901–2016). The change in temperature for the continental United States for this period is also 1.8°F. This period is now the warmest in the history of modern civilization.
3. Recent years have seen record-breaking, climate-related weather extremes, and the last four years have been the warmest years on record for the globe. These trends are expected to continue over climate timescales.
4. Changes in the characteristics of extreme events are particularly important for human safety, infrastructure, agriculture, water quality and quantity, and natural ecosystems. Some extremes have already become more frequent, intense, or of longer duration, and many extremes are expected to continue to increase or worsen, presenting substantial challenges.
5. Heavy precipitation, as either rainfall or snowfall, is increasing in intensity and frequency across the United States and globally and is expected to continue to increase. The largest observed changes in extreme precipitation in the United States have occurred in the Northeast and the Midwest.
6. Heat waves have become more frequent globally since 1900 and in the United States since the 1960s, while extreme cold temperatures and cold waves have become less frequent.
7. Annual trends toward earlier spring snowmelt and reduced snowpack are already affecting water resources in various parts of the world (e.g., the western United States), with adverse effects for fisheries and electricity generation. These trends are expected to continue.
8. The incidence of large forest fires in the western contiguous United States and Alaska has increased since the early 1980s and is projected to further increase in those regions as the climate warms, with profound changes to regional ecosystems.
9. Tropical cyclones (e.g., hurricanes, typhoons) are likely to become more intense with larger precipitation over the coming decades.
10. Global average sea level has risen by about 7–8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993.
11. Human-caused climate change has made a substantial contribution to this rise since 1900, contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years.
12. Global sea level rise is already affecting many coastal areas around the world; for example, the incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities in the United States.
13. Global average sea levels are expected to continue to rise—by at least several inches in the next 15 years and by 1 to 4 feet by 2100. A rise of as much as 8 feet by 2100 cannot be ruled out because of uncertainties about the decline of the west Antarctica ice sheet.
14. Many lines of evidence demonstrate that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. Over the last century, there are no convincing alternative explanations supported by the extent of the observational evidence. Solar output changes and internal natural variability can only contribute marginally to the observed changes in climate over the last century, and there is no convincing evidence for natural cycles in the observational record that could explain the observed changes in climate.
15. The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reductions in greenhouse gas emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century.
16. With significant reductions in greenhouse gas emissions, the increase in annual average global temperature could be limited to 3.6°F (2°C) or less.
17. The atmospheric carbon dioxide (CO2) concentration is now over 405 parts per million (ppm) globally-and annually-averaged, a level that last occurred about 3 million years ago, when both global average temperature and sea level were significantly higher than today. The highest level of atmospheric carbon dioxide (CO2) concentration in human history, 410 ppm, was measured in April 2018.
18. Continued growth in CO2 emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years.
19. The observed increase in carbon emissions over the past 15–20 years has been consistent with higher emissions pathways. In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-intensive, but then increased in 2016.
20. Without significant cuts to emissions, annual average global temperatures will almost certainly rise beyond 2°C (3.6°F) by the end of the century, but there are still emission pathways which could enable the world to remain below this level of warming.