Some of the events shown as icons on the map are direct manifestations of a widespread and long-term trend toward warmer global temperatures as projected by models of a changing climate. On the map, these "fingerprints" of climate change are indicated with yellow icons.
The following events are identified as global warming fingerprints:
The map highlights places that have recently experienced record warmth in regions with a century-long warming trend (1901-1996). Frequent and severe heat waves lead to increases in heat-related illness and death, especially in urban areas and among the elderly, the young, the ill, and the poor.
Hotspot Selection Criteria: Hotspots in this category illustrate notably warm periods or heat waves within the last few years. Candidate events were initially gathered from news reports and climate bulletins. We then looked at National Climatic Data Center (http://www.ncdc.noaa.gov/onlineprod/gsod/climvis/gsod.html) and NASA/GISS (http://www.giss.nasa.gov/data/update/csci/) websites to obtain the actual temperature records for the city or region to: a) verify the occurrence of the heat wave or warm period; and b) place it in the context of the longer-term temperature record. We avoided using one-day records because of the inherent probability that a maximum temperature record could be broken on any given day due to internal climate variability. Only those events that were notable either in duration or geographic extent were included. Whenever possible, periods at least as long as a month (e.g., hottest March ever on record) were chosen. We also included only those locations that fall within a region that showed a warming trend over the last century, as reported in Annex A of the IPCC?s Regional Impacts of Climate Change (1998).
Warmer temperatures increase melting of mountain glaciers, increase ocean heat content, and cause ocean water to expand. Largely as a result of these effects, global sea level has risen 4 to 10 inches (10-25 cm) over the past 100 years. With additional warming, sea level is projected to rise from half a foot to 3 feet (15-92 cm) more during the next 100 years. On average, 50 to 100 feet (15-30 meters) of beach are lost for every foot (0.3 meters) of sea-level rise. Local land subsidence (sinking) and/or uplift due to geologic forces and coastal development will also affect the rate of coastal land loss.
Hotspot Selection Criteria: The sea-level rise (SLR) data were confirmed by published journal articles. We did not include places where there were tide gauge records of a rising sea level but no information about land inundation consequences (e.g., Buenos Aires, where the shoreline is raised/hardened and thus protected from inundation); places where there was evidence of land erosion but no SLR records (e.g., the island of Geneva and other Caribbean islands); and places where subsidence or other factors (e.g., changes in river sediment deposition) were clearly the dominating influence on land erosion (e.g., New Orleans and Victoria, Egypt). Although the inundation records for the South Pacific islands are based on anecdotal evidence from local residents, we included them because these accounts are often the best and only evidence available in these very vulnerable small island nations.
Over the past 150 years, the majority of mountain glaciers monitored have been shrinking. Many glaciers at lower latitudes are now disappearing, and scientists predict that, under some plausible warming scenarios, the majority of glaciers will be gone by the year 2100. As glaciers continue to shrink, summer water flows will drop sharply, disrupting an important source of water for irrigation and power in many areas that rely on mountain watersheds.
Hotspot Selection Criteria: The data come from published scientific articles or personal communication with researchers. In cases where individual glaciers are cited, we confirmed, based on available data, that the majority of glaciers in that region are in retreat. Many of the events were outlined in an unpublished transcript of the 1998 Walter B. Langbein Memorial Lecture at the 1998 spring meeting of the American Geophysical Union, generously provided by Dr. Mark Meier, University of Colorado.
Parts of Canada, Alaska, Siberia, and the Antarctic have been experiencing warming well above the global average for the past few decades. This trend fits climate model predictions for a world with increasing levels of greenhouse gases. Melting permafrost is forcing the reconstruction of roads, airports, and buildings and is increasing erosion and the frequency of landslides. Reduced sea ice and ice shelves, changes in snowfall, and pest infestations have affected native plants and animals that provide food and resources to many people.
Hotspot Selection Criteria: This category includes events linked to the warming temperatures observed in parts of Alaska, Canada, Siberia, and Antarctica, as published in journal articles and technical reports. Information on the break-up of the Antarctica Peninsula ice shelves also comes from the National Snow and Ice Data Center (NSIDC) website. Dr. Ted Scambos at NSIDC confirmed that the disintegration events listed on the map were unusual given our current understanding of the mechanics of ice shelves. Very large icebergs calving off other Antarctic ice shelves (e.g., Ross) were not included because they are considered to be part of the ?normal? calving process.