Menu
Home
Water
Energy and Environment
Global Change
- Climate change
- Sea level
- Tectonics
- Ecosystem ecology
- Paleoecology
- Remote sensing of the environment
- Earth system modeling
Environment-Society Interactions
Environmental Literacy
Student Projects
Global Change
Climate Change
Yu, Sahagian, Felzer, Briggs
Earth's climate has had a profound effect on the development of society and modern economic systems. Social systems and what we consider civilization emerged throughout the Holocene in the last ten thousand years during a time of relative climate stability. Prior to that, glacial-interglacial cycles caused changes in regional climate that forced migration of ecosystems and their accompanying animals, including humans. Still, over the lat million years, global climate has oscillated with atmospheric CO2 concentrations alternating between remarkably fixed bounds of 180 ppm (glacial times) and 280 ppm (interglacials). Beginning with the industrial revolution, modern society has now rapidly increased that concentration to 386 ppm, far beyond the envelope of the natural climate system, and it is being driven to increase at a rate of 2 ppm/yr, but this rate is accelerating due to increased combustion of fossil fuels globally. In order to predict the alteration of global and regional climate to this anthropogenic forcing, it is necessary to understand the processes that control the sensitivity of the climate system to atmospheric chemistry, land cover, and ice extent. Toward that end, Lehigh faculty are exploring the history of paleoclimate through its record in peat bogs, rocks, and microbial assemblages. In addition, numerical models are being developed to help project the global and regional manifestations of climate change based on a suite of scenarios of emissions and land use. B y learning from the past, and projecting into the future, Lehigh research in this area can help prepare future societies for expected (and even surprising) climate changes to reduce vulnerability of natural and social systems through design of a suite of policies that will 1) mitigate the extent of climate change, 2) adapt human infrastructure to what cannot be mitigated, and 3) prepare to simply do without those environmental goods and services that are lost due to insufficient mitigation and adaptation.
Sea Level
Sahagian
One of the most serious threats to modern society imposed by climate change is the impact of sea level rise on coastal infrastructure and ecosystems. Sea level is the elevation of the Earth's sea surface relative to its land surface, and has varied by hundreds of meters over geologic time, depositing deep marine rocks in the middle of what are now continents, for instance. Relative sea level is the elevation of the sea surface relative to a specific point on the shoreline, and can be measured using tides gauges that were deployed throughout the 20th century. Eustatic sea level is the relative volume of the Earth ocean basins to the Earth's ocean water, but is much more difficult to measure. However, the two are only different on timescales on which the land surface deforms. As such, the modern rate of melting ice and thermal expansion of ocean water leads to both relative and eustatic sea level rise. Over the 20th century, the rate has been 1.5-2 mm/yr, but this is accelerating. Part of this acceleration is due to quickening glacial melting and ocean warming, while part of it is due to reduction in the rate of dam-building relative to the 20th century, during which tide gauge measurements exist. The latter suggests that we have been artificially masking the true rate of sea level rise by building dams in the 20th century, and that projections of 21st century sea level rise that are based on 20th century tide gauge observations are underestimated so that we may actually see as much as a doubling of sea level rise even without the increase in melting or warming.