GLOBAL WARMING

Global Warming and its Effect on the Water System in NYC by 2050

Abstract

The present atmospheric carbon dioxide concentration is the highest in at least the past 420,000 years (Falkowski 2000; Petit, et al. 1999) and probably the past 20 million years (Pagani, et al. 1999). The Intergovernmental Panel on Climate Change (IPCC)2 projects that by the year 2100, CO2 concentrations may increase by as much as 350% and the average global temperature may rise by as much as 11° F under business-as-usual scenarios (2001:12-13). By comparison, in the last ice age about 20,000 years ago, average global temperatures were only about 9° F cooler than present. At that time, ice over 2 miles thick covered present-day Canada, stretching south over the upper Midwest and New England. Human greenhouse gas emissions may increase average global temperatures by an equal order of magnitude. One of the most serious consequences of global warming may be on the world's water supply. If you've read about increased vapor in the clouds that's theorized to cause the change in the earth's surface temperature, you may wonder why that would impact our water supplies.

Global Warming and its Effect on the Water System in NYC by 2050

Introduction

The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC; Albritton et al. 2001) has recently concluded, as very likely, that (among other things) 1) global average surface temperature has increased over the twentieth century by ~0.6°C; 2) global ocean heat content has increased since the late 1950s; 3) the 1990s represent the warmest decade of the twentieth century; 4) there has been a reduction of ~2 weeks in the annual duration of lake ice cover in the Northern Hemisphere; and 5) most of the warming of the last 50 yr is attributable to human emissions of greenhouse gases.

Continued anthropogenic influences on the earth's climate will likely contribute to significant regional variability in temperature and precipitation changes during the twenty-first century. One area of concern is the heavily populated Great Lakes region of North America and the affect these large bodies of water will have on regional climate and hydrology. Because of their thermal capacity and climatological setting, the Great Lakes generate large quantities of lake-effect snowfall along their leeward margins during late autumn and winter when cold continental air masses travel across the ice-free lake surfaces.

The relative warmth of the lakes during this time of year, as compared to air temperatures, destabilizes the overlying atmosphere through vertical fluxes of heat and moisture from water to air. Heavy lake-effect snows can be natural hazards to life and property, affect air and surface traffic, create multimillion-dollar recreational industries, and influence agricultural activities, water supplies, and hydroelectric generation.

Using data from over 1230 weather stations around the Great Lakes, Norton and Bolsenga (1993) found significant increases in lake-effect snow between 1951 and 1980. This finding confirmed the earlier work of Eichenlaub (1970) and Braham and Dungey (1984) who also noted increases in lake-effect ...