Global Warming And the Planetary Water Cycle Ruth Curry Woods Hole Oceanographic Institution Ruth Curry Woods Hole Oceanographic Institution Global Warming And the Planetary Water Cycle

Planet Earth is warming

ppm The link between greenhouse gas concentrations and surface temperatures is indisputable You are here 379

Penetration of ocean warming signal Courtesy of Tim Barnett (Scripps)

In the last half of the 20 th century, it is clear that the world oceans are heating up. Levitus et al. Science, 2005 The oceans have absorbed about 20 times more heat than the atmosphere since 1955 Oceans 14.5 x J Atmosphere 0.7 x J

Global climate change is not just about temperature…. A snowman’s perspective

It is expected that the planetary water cycle – Evaporation/Condensation/Precipitation and Freezing/Melting – will be altered as a result of global warming. There is ample evidence of it already happening…

Precipitation patterns are changing on global scales… …most measurements of precipitation are made over land areas

Unprecedented warmth of SST in Indian, W. Pacific and Atlantic Oceans is driving shifts in precipitation patterns…

Salinity changes are the fingerprint of increasing evaporation from the low latitude oceans….. Low latitude surface waters have become markedly more saline Water masses formed at high latitudes have become fresher … and freshwater being added to the oceans at high latitudes.

Atlantic Ocean Salinity Changes 1990s compared to 1960s from Curry et al. Nature (2003)

Increased river discharge Increased precipitation appears to be the dominant factor elevating continental runoff into the Arctic basins which is contributing to salinity decreases in the North Atlantic

NASA Goddard Space Flight Center Summer Arctic Sea Ice is shrinking and thinning

NY Times June 8, 2004 Greenland is melting

Antarctica is still gaining mass, but its ice shelves are growing unstable, increasing the surge of land ice into the ocean

Ocean warming and melting land ice are causing sea level to rise

Too much freshwater added to key locations could disrupt ocean circulation and its transport of heat

Conveyor ON

Conveyor OFF

NorthSouth Denmark Strait NorthSouth Denmark Strait … and changing the density of waters that feed the overflows – the first steps toward slowing the Ocean Conveyor Since the 1990s, freshwater has been accumulating in the surface layers of the Nordic Seas …

Freshwater storage and net flux anomalies Curry & Mauritzen, Science (2005) km km km Sv 10,000 km 3

This does not mean the Ocean Conveyor will shut down, but that conditions are moving in a direction favorable for doing so. Conveyor ONConveyor OFF

Earth’s freshwater balance is being pushed out of kilter by rising GHG concentrations, and this is expected to amplify in the foreseeable future. A scientist’s perspective: Sea level rise and freshwater resources will be issues of increasing urgency confronting ecosystems and economies in the 21 st century. It is not a question of “if”…. but rather a question of “when” and “how fast”

Curb fossil fuel emissions – as soon as possible