Overview of Climate Change Throughout Earth History Overview of Climate Change Throughout Earth History During the Phanerozoic (600 Ma), climate fluctuated between During the Phanerozoic (600 Ma), climate fluctuated between

What were the possible causes of warm-cool modes during the Phanerozoic? What were the possible causes of warm-cool modes during the Phanerozoic? (think plate tectonics) — which would have altered ocean and atmosphere circulation — which would have altered ocean and atmosphere circulation

Proxy data used to study Phanerozoic climates:  e.g., halite, gypsum; indicate that a warm-dry climate prevailed when and where these rocks formed  e.g., halite, gypsum; indicate that a warm-dry climate prevailed when and where these rocks formed  indicate a warm, humid climate  indicate a warm, humid climate  old glacial deposits preserved in ancient rocks  old glacial deposits preserved in ancient rocks

Cretaceous period (100 Ma): temperatures were continents were located existed

Tertiary period— uplift of Rocky Mtns. and Himalayas

Quaternary period (~1.8 Ma to present): Pleistocene epoch (1.8 Ma to 11.5 Ka) -- climate marked by a Pleistocene epoch (1.8 Ma to 11.5 Ka) -- climate marked by a

Pleistocene (cont’d): 1.glacials: ~ 90,000 yr interglacials: ~10,000 yr 1.glacials: ~ 90,000 yr interglacials: ~10,000 yr a. continental ice sheets up to 3 km thick covered N. Am. And N. Eurasia a. continental ice sheets up to 3 km thick covered N. Am. And N. Eurasia (LGM): 18 Ka (LGM): 18 Ka

b. expanded in the Rocky Mountains and other parts of the world b. expanded in the Rocky Mountains and other parts of the world c. in the N. Hemisphere ranged ~10º latitude further south than present c. in the N. Hemisphere ranged ~10º latitude further south than present d. oceans were ~2º C cooler than today d. oceans were ~2º C cooler than today e.air temperatures 1-12º C cooler, depending on location f. e.air temperatures 1-12º C cooler, depending on location f.

g. melting of ice sheets began ~17 Ka and continued at an uneven pace g. melting of ice sheets began ~17 Ka and continued at an uneven pace

the YD started many climate scientists believe that the abrupt cooling and warming at the beginning and end of the YD was cause by a shut- down of the many climate scientists believe that the abrupt cooling and warming at the beginning and end of the YD was cause by a shut- down of the

cross-section view of ocean circulation in the Atlantic: cross-section view of ocean circulation in the Atlantic: --the 3-dimensional circulation of the oceans; it is driven by salinity and temperature differences

the THC and surface ocean currents combine to create a of three-dimensional oceanic circulation the THC and surface ocean currents combine to create a of three-dimensional oceanic circulation

Downwelling of cold, salty water in the North Atlantic ‘pulls’ surface waters further north than they normally would travel; this is termed Downwelling of cold, salty water in the North Atlantic ‘pulls’ surface waters further north than they normally would travel; this is termed

downwelling of water is controlled by water density downwelling of water is controlled by water density Is the Atlantic Heat Pump constant? NO! have been blamed for the rapid temp. changes of the YD have been blamed for the rapid temp. changes of the YD if less dense freshwater is added to the North Atlantic, it will not sink as rapidly, resulting in a if less dense freshwater is added to the North Atlantic, it will not sink as rapidly, resulting in a

What could cause freshwater inputs to the North Atlantic to increase? What could cause freshwater inputs to the North Atlantic to increase?

during the Hypsithermal than today during the Hypsithermal than today

temps were warmer than present in some areas

climate much colder than present (though not a true ‘ice age’) glaciers advanced in Europe, N. America, Africa, New Zealand Vikings abandoned Greenland settlements climate much colder than present (though not a true ‘ice age’) glaciers advanced in Europe, N. America, Africa, New Zealand Vikings abandoned Greenland settlements

[from 13.6º C to 14.4º C (56.8º F to 57.6º F)]

From 2007 IPCC Report

Over long time periods, climate is not stable! Over long time periods, climate is not stable! Statements about climate depend on the time scale you are considering. Statements about climate depend on the time scale you are considering.

Deep thoughts: Is the recent warming caused by increased greenhouse gases (CO 2 ) in the atmosphere? What should be done, if anything, to address global warming? How much warming will occur in the next yr? How much warming will occur in the next yr?