Decades of scientific research have shown that climate can change from both natural and anthropogenic causes. The Geological Society of America (GSA) concurs with assessments by the National Academies of Science (2005), the National Research Council (2006), and the Intergovernmental Panel on Climate Change (IPCC, 2007) that global climate has warmed and that human activities (mainly greenhouse‐gas emissions) account for most of the warming since the middle 1900s. If current trends continue, the projected increase in global temperature by the end of the twentyfirst century will result in large impacts on humans and other species. Addressing the challenges posed by climate change will require a combination of adaptation to the changes that are likely to occur and global reductions of CO2 emissions from anthropogenic sources.In the supporting text, despite what you may have heard elsewhere, they assert:
Scientific advances in the first decade of the 21st century have greatly reduced previous uncertainties about the amplitude and causes of recent global warming.The statement goes on to briefly summarize the evidence in question. It also summarizes consequences as follows:
The projected changes involve risk to humans and other species:How much of that did you read in your newspaper lately?
- (1) continued shrinking of Arctic sea ice with effects on native cultures and ice-dependent biota;
- (2) less snow accumulation and earlier melt in mountains, with reductions in spring and summer runoff for agricultural and municipal water;
- (3) disappearance of mountain glaciers and their late-summer runoff;
- (4) increased evaporation from farmland soils and stress on crops;
- (5) greater soil erosion due to increases in heavy convective summer rainfall;
- (6) longer fire seasons and increases in fire frequency;
- (7) severe insect outbreaks in vulnerable forests;
- (8) acidification of the global ocean; and
- (9) fundamental changes in the composition, functioning, and biodiversity of many terrestrial and marine ecosystems.
- In addition, melting of Greenland and West Antarctic ice (still highly uncertain as to amount), along with thermal expansion of seawater and melting of mountain glaciers and small ice caps, will cause substantial future sea-level rise along densely populated coastal regions, inundating farmland and dislocating large populations. Because large, abrupt climatic changes occurred within spans of just decades during previous ice-sheet fluctuations, the possibility exists for rapid future changes as ice sheets become vulnerable to large greenhouse-gas increases.
- Finally, carbon-climate model simulations indicate that 10–20% of the anthropogenic CO2 “pulse” could stay in the atmosphere for thousands of years, extending the duration of fossil-fuel warming and its effects on humans and other species. The acidification of the global ocean and its effects on ocean life are projected to last for tens of thousands of years.