Here's example on how to create a WMS layer instance using the Open Source JavaScript library OpenLayers. The possible values for layers can be found in the expandable list below.

  var wms = new OpenLayers.Layer.WMS(
    "Population Density",
    "http://sedac.ciesin.columbia.edu/geoserver/gwc/service/wms",
    {layers: 'gpw-v3:gpw-v3-population-density_2000'}
  );

Gridded Species Distribution (1) View WMS Layers

• (1) Global Amphibians Family Richness Grids

  • species-v1-global-amphibian-family-richness

Global Fertilizer and Manure (4) View WMS Layers

• (1) Phosphorus Fertilizer Application

  • ferman-v1-phosphorus-fertilizer-application

• (1) Phosphorus in Manure Production

  • ferman-v1-phosphorus-in-manure-production

• (1) Nitrogen in Manure Production

  • ferman-v1-nitrogen-in-manure-production

• (1) Nitrogen Fertilizer Application

  • ferman-v1-nitrogen-fertilizer-application

Last of the Wild (3) View WMS Layers

• (1) Global Human Influence Index (Geographic)

  • wildareas-v2-human-influence-index-geographic

• (1) Last of the Wild (Geographic)

  • wildareas-v2-last-of-the-wild-geographic

• (1) Global Human Footprint (Geographic)

  • wildareas-v2-human-footprint-geographic

Global Agricultural Lands (2) View WMS Layers

• (1) Pastures

  • aglands-pastures-2000

• (1) Croplands

  • aglands-croplands-2000

Environmental Sustainability Index (22) View WMS Layers

• (22) Environmental Sustainability Index

  • esi-environmental-sustainability-index-2005
  • esi-environmental-sustainability-index-2005_air-quality
  • esi-environmental-sustainability-index-2005_biodiversity
  • esi-environmental-sustainability-index-2005_eco-efficiency
  • esi-environmental-sustainability-index-2005_environ-governance
  • esi-environmental-sustainability-index-2005_environ-health
  • esi-environmental-sustainability-index-2005_greenhouse-gas-emissions
  • esi-environmental-sustainability-index-2005_human-sustenance
  • esi-environmental-sustainability-index-2005_land
  • esi-environmental-sustainability-index-2005_nat-disaster-vulnerability
  • esi-environmental-sustainability-index-2005_nat-resource-mgmt
  • esi-environmental-sustainability-index-2005_particip-international-collaborate
  • esi-environmental-sustainability-index-2005_private-sector-response
  • esi-environmental-sustainability-index-2005_reduce-air-pollution
  • esi-environmental-sustainability-index-2005_reduce-ecosystem-stress
  • esi-environmental-sustainability-index-2005_reduce-pop-press
  • esi-environmental-sustainability-index-2005_reduce-trans-environ-press
  • esi-environmental-sustainability-index-2005_reduce-waste-consump-press
  • esi-environmental-sustainability-index-2005_reduce-water-stress
  • esi-environmental-sustainability-index-2005_science-tech
  • esi-environmental-sustainability-index-2005_water-quality
  • esi-environmental-sustainability-index-2005_water-quantity

U.S. Census Grids (80) View WMS Layers

• (22) Summary File 1

  • usgrid-summary-file1-2000_usa-housingunitsf1density-2000
  • usgrid-summary-file1-2000_usa-pct1personhousing-2000
  • usgrid-summary-file1-2000_usa-pctasian-2000
  • usgrid-summary-file1-2000_usa-pctblack-2000
  • usgrid-summary-file1-2000_usa-pctfemaleheadhousing-2000
  • usgrid-summary-file1-2000_usa-pcthispanic-2000
  • usgrid-summary-file1-2000_usa-pctnativeamerican-2000
  • usgrid-summary-file1-2000_usa-pctnonhispblack-2000
  • usgrid-summary-file1-2000_usa-pctnonhispwhite-2000
  • usgrid-summary-file1-2000_usa-pctoccupiedhousingsf1-2000
  • usgrid-summary-file1-2000_usa-pctownerhousing-2000
  • usgrid-summary-file1-2000_usa-pctpacificisland-2000
  • usgrid-summary-file1-2000_usa-pctpop18to24-2000
  • usgrid-summary-file1-2000_usa-pctpop1to4-2000
  • usgrid-summary-file1-2000_usa-pctpop25to64-2000
  • usgrid-summary-file1-2000_usa-pctpop5to17-2000
  • usgrid-summary-file1-2000_usa-pctpop65to79-2000
  • usgrid-summary-file1-2000_usa-pctpop80andup-2000
  • usgrid-summary-file1-2000_usa-pctpopunder1-2000
  • usgrid-summary-file1-2000_usa-pctvacanthousing-2000
  • usgrid-summary-file1-2000_usa-pctwhite-2000
  • usgrid-summary-file1-2000_usa-popsf1density-2000

• (18) Summary File 3

  • usgrid-summary-file3-2000_usa-householdsdensity-2000
  • usgrid-summary-file3-2000_usa-housingunitsf3density-2000
  • usgrid-summary-file3-2000_usa-pcteducationbahigher-2000
  • usgrid-summary-file3-2000_usa-pcteducationhshigher-2000
  • usgrid-summary-file3-2000_usa-pctforeign-2000
  • usgrid-summary-file3-2000_usa-pcthouseholdlinguisticisolation-2000
  • usgrid-summary-file3-2000_usa-pcthousingbuilt50to69-2000
  • usgrid-summary-file3-2000_usa-pcthousingbuilt70to89-2000
  • usgrid-summary-file3-2000_usa-pcthousingbuilt90to00-2000
  • usgrid-summary-file3-2000_usa-pcthousingbuiltbefore50-2000
  • usgrid-summary-file3-2000_usa-pctoccupiedhousingnocar-2000
  • usgrid-summary-file3-2000_usa-pctoccupiedhousingsf3-2000
  • usgrid-summary-file3-2000_usa-pctpop25andover-2000
  • usgrid-summary-file3-2000_usa-pctpopbelow200pctpovlevel-2000
  • usgrid-summary-file3-2000_usa-pctpopbelow50pctpovlevel-2000
  • usgrid-summary-file3-2000_usa-pctpopbelowpovlevel-2000
  • usgrid-summary-file3-2000_usa-pctpoppovleveldetermined-2000
  • usgrid-summary-file3-2000_usa-popsf3density-2000

• (18) Summary File 3: Metropolitan Statistical Areas

  • usgrid-summary-file3-2000-msa_householdsdensity-2000
  • usgrid-summary-file3-2000-msa_housingunitsf3density-2000
  • usgrid-summary-file3-2000-msa_pcteducationbahigher-2000
  • usgrid-summary-file3-2000-msa_pcteducationhshigher-2000
  • usgrid-summary-file3-2000-msa_pctforeign-2000
  • usgrid-summary-file3-2000-msa_pcthouseholdlinguisticisolation-2000
  • usgrid-summary-file3-2000-msa_pcthousingbuilt50to69-2000
  • usgrid-summary-file3-2000-msa_pcthousingbuilt70to89-2000
  • usgrid-summary-file3-2000-msa_pcthousingbuilt90to00-2000
  • usgrid-summary-file3-2000-msa_pcthousingbuiltbefore50-2000
  • usgrid-summary-file3-2000-msa_pctoccupiedhousingnocar-2000
  • usgrid-summary-file3-2000-msa_pctoccupiedhousingsf3-2000
  • usgrid-summary-file3-2000-msa_pctpop25andover-2000
  • usgrid-summary-file3-2000-msa_pctpopbelow200pctpovlevel-2000
  • usgrid-summary-file3-2000-msa_pctpopbelow50pctpovlevel-2000
  • usgrid-summary-file3-2000-msa_pctpopbelowpovlevel-2000
  • usgrid-summary-file3-2000-msa_pctpoppovleveldetermined-2000
  • usgrid-summary-file3-2000-msa_popsf3density-2000

• (22) Summary File 1: Metropolitan Statistical Areas

  • usgrid-summary-file1-2000-msa_housingunitsf1density-2000
  • usgrid-summary-file1-2000-msa_pct1personhousing-2000
  • usgrid-summary-file1-2000-msa_pctasian-2000
  • usgrid-summary-file1-2000-msa_pctblack-2000
  • usgrid-summary-file1-2000-msa_pctfemaleheadhousing-2000
  • usgrid-summary-file1-2000-msa_pcthispanic-2000
  • usgrid-summary-file1-2000-msa_pctnativeamerican-2000
  • usgrid-summary-file1-2000-msa_pctnonhispblack-2000
  • usgrid-summary-file1-2000-msa_pctnonhispwhite-2000
  • usgrid-summary-file1-2000-msa_pctoccupiedhousingsf1-2000
  • usgrid-summary-file1-2000-msa_pctownerhousing-2000
  • usgrid-summary-file1-2000-msa_pctpacificisland-2000
  • usgrid-summary-file1-2000-msa_pctpop18to24-2000
  • usgrid-summary-file1-2000-msa_pctpop1to4-2000
  • usgrid-summary-file1-2000-msa_pctpop25to64-2000
  • usgrid-summary-file1-2000-msa_pctpop5to17-2000
  • usgrid-summary-file1-2000-msa_pctpop65to79-2000
  • usgrid-summary-file1-2000-msa_pctpop80andup-2000
  • usgrid-summary-file1-2000-msa_pctpopunder1-2000
  • usgrid-summary-file1-2000-msa_pctvacanthousing-2000
  • usgrid-summary-file1-2000-msa_pctwhite-2000
  • usgrid-summary-file1-2000-msa_popsf1density-2000

Global Rural-Urban Mapping Project (9) View WMS Layers

• (1) Land and Geographic Unit Area Grids

  • grump-v1-land-geographic-unit-area

• (3) Population Count Grid

  • grump-v1-population-count_1990
  • grump-v1-population-count_1995
  • grump-v1-population-count_2000

• (1) Urban Extents Grid

  • grump-v1-urban-extents

• (3) Population Density Grid

  • grump-v1-population-density_1990
  • grump-v1-population-density_1995
  • grump-v1-population-density_2000

• (1) Settlement Points

  • grump-v1-settlement-points

Natural Disaster Hotspots (25) View WMS Layers

• (1) Global Earthquake Proportional Economic Loss Risk Deciles

  • ndh-earthquake-proportional-economic-loss-risk-deciles

• (1) Global Cyclone Hazard Frequency and Distribution

  • ndh-cyclone-hazard-frequency-distribution

• (1) Global Drought Mortality Risks and Distribution

  • ndh-drought-mortality-risks-distribution

• (1) Global Flood Mortality Risks and Distribution

  • ndh-flood-mortality-risks-distribution

• (1) Global Earthquake Total Economic Loss Risk Deciles

  • ndh-earthquake-total-economic-loss-risk-deciles

• (1) Global Drought Hazard Frequency and Distribution

  • ndh-drought-hazard-frequency-distribution

• (1) Global Cyclone Total Economic Loss Risk Deciles

  • ndh-cyclone-total-economic-loss-risk-deciles

• (1) Global Landslide Hazard Distribution

  • ndh-landslide-hazard-distribution

• (1) Global Volcano Total Economic Loss Risk Deciles

  • ndh-volcano-total-economic-loss-risk-deciles

• (1) Global Flood Total Economic Loss Risk Deciles

  • ndh-flood-total-economic-loss-risk-deciles

• (1) Global Earthquake Mortality Risks and Distribution

  • ndh-earthquake-mortality-risks-distribution

• (1) Global Volcano Mortality Risks and Distribution

  • ndh-volcano-mortality-risks-distribution

• (1) Global Landslide Total Economic Loss Risk Deciles

  • ndh-landslide-total-economic-loss-risk-deciles

• (1) Global Cyclone Proportional Economic Loss Risk Deciles

  • ndh-cyclone-proportional-economic-loss-risk-deciles

• (1) Global Earthquake Hazard Distribution - Peak Ground Acceleration

  • ndh-earthquake-distribution-peak-ground-acceleration

• (1) Global Cyclone Mortality Risks and Distribution

  • ndh-cyclone-mortality-risks-distribution

• (1) Global Landslide Mortality Risks and Distribution

  • ndh-landslide-mortality-risks-distribution

• (1) Global Drought Proportional Economic Loss Risk Deciles

  • ndh-drought-proportional-economic-loss-risk-deciles

• (1) Global Volcano Proportional Economic Loss Risk Deciles

  • ndh-volcano-proportional-economic-loss-risk-deciles

• (1) Global Flood Proportional Economic Loss Risk Deciles

  • ndh-flood-proportional-economic-loss-risk-deciles

• (1) Global Earthquake Hazard Frequency and Distribution

  • ndh-earthquake-frequency-distribution

• (1) Global Landslide Proportional Economic Loss Risk Deciles

  • ndh-landslide-proportional-economic-loss-risk-deciles

• (1) Global Volcano Hazard Frequency and Distribution

  • ndh-volcano-hazard-frequency-distribution

• (1) Global Drought Total Economic Loss Risk Deciles

  • ndh-drought-total-economic-loss-risk-deciles

• (1) Global Flood Hazard Frequency and Distribution

  • ndh-flood-hazard-frequency-distribution

Environmental Performance Index (11) View WMS Layers

• (11) Environmental Performance Index

  • epi-environmental-performance-index-2010
  • epi-environmental-performance-index-2010_agriculture
  • epi-environmental-performance-index-2010_air-pollution-effects-on-ecosystems
  • epi-environmental-performance-index-2010_air-pollution-effects-on-human-health
  • epi-environmental-performance-index-2010_biodiversity-and-habitat
  • epi-environmental-performance-index-2010_climate-change
  • epi-environmental-performance-index-2010_environmental-burden-of-disease
  • epi-environmental-performance-index-2010_fisheries
  • epi-environmental-performance-index-2010_forestry
  • epi-environmental-performance-index-2010_water-effects-on-ecosystems
  • epi-environmental-performance-index-2010_water-effects-on-human-health

Gridded Population of the World (15) View WMS Layers

• (3) Population Count Grid Future Estimates

  • gpw-v3-population-count-future-estimates_2005
  • gpw-v3-population-count-future-estimates_2010
  • gpw-v3-population-count-future-estimates_2015

• (3) Population Count Grid

  • gpw-v3-population-count_1990
  • gpw-v3-population-count_1995
  • gpw-v3-population-count_2000

• (1) Land and Geographic Unit Area Grids

  • gpw-v3-land-geographic-unit-area

• (3) Population Density Grid

  • gpw-v3-population-density_1990
  • gpw-v3-population-density_1995
  • gpw-v3-population-density_2000

• (1) Coastlines

  • gpw-v3-coastlines

• (1) Centroids

  • gpw-v3-centroids

• (3) Population Density Grid Future Estimates

  • gpw-v3-population-density-future-estimates_2005
  • gpw-v3-population-density-future-estimates_2010
  • gpw-v3-population-density-future-estimates_2015

Poverty Mapping (2) View WMS Layers

• (1) Global Subnational Prevalence of Child Malnutrition

  • povmap-global-subnational-prevalence-child-malnutrition

• (1) Global Subnational Infant Mortality Rates

  • povmap-global-subnational-infant-mortality-rates_2000

Anthropogenic Biomes (1) View WMS Layers

• (1) Anthropogenic Biomes of the World

  • anthromes-anthropogenic-biomes-world-v1

Global Reservoir and Dam (2) View WMS Layers

• (1) Reservoirs

  • grand-v1-reservoirs-rev01

• (1) Dams

  • grand-v1-dams-rev01

IPCC Assessment (2) View WMS Layers

• (1) Fourth Assessment Report (AR4) Observed Climate Change Impacts

  • ipcc-assess-ar4-observed-climate-impacts

• (1) Synthetic Assessment of Global Distribution of Vulnerability to Climate Change

  • ipcc-assess-synthetic-vulnerability-climate-2005-2050-2100

Climate Effects on Food Supply (1) View WMS Layers

• (1) Effects of Climate Change on Global Food Production from SRES Emissions and Socioeconomic Scenarios

  • crop-climate-effects-climate-global-food-production