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Chapter 14: Climate Change The earth’s changing climate The earth’s changing climate Possible causes of climatic change Possible causes of climatic change Global warming Global warming

Why Climate Change Matters Why should you be aware of climate change? Why should you be aware of climate change? Climate is changing and your generation will be the one to make or break it Climate is changing and your generation will be the one to make or break it Climate change (whether nature or manmade) will directly affect you! Climate change (whether nature or manmade) will directly affect you!

Determining Past Climates How do we know what past climates were like? How do we know what past climates were like? Fossil evidence Fossil evidence Fossils of tundra plants in New England suggest a colder climate Fossils of tundra plants in New England suggest a colder climate Ocean sediment cores Ocean sediment cores Certain animals must have lived in a range of ocean temperatures Certain animals must have lived in a range of ocean temperatures Oxygen isotope ratios Oxygen isotope ratios Differing isotope counts mean differing temperatures Differing isotope counts mean differing temperatures

Determining Past Climates How do we know what past climates were like? How do we know what past climates were like? Ice cores Ice cores Sulfuric acid in ice cores Sulfuric acid in ice cores Oxygen isotopes (cold the air, the more isotopes) Oxygen isotopes (cold the air, the more isotopes) Bubbles in the ice contain trapped composition of the past atmospheres Bubbles in the ice contain trapped composition of the past atmospheres Dendrochronology Dendrochronology Examining tree rings to see growth patterns Examining tree rings to see growth patterns

Climate Through the Ages Much of Earth’s history was warmer than today by as much as 15°C Much of Earth’s history was warmer than today by as much as 15°C Ice age Ice age Most recently 2.5 m.y.a. Most recently 2.5 m.y.a. Beginning marked by glaciers in North America Beginning marked by glaciers in North America Interglacial periods (between glacial advances) Interglacial periods (between glacial advances) When glaciers were at their max (18,000 – 22,000 years ago) sea level 395 feet lower than today When glaciers were at their max (18,000 – 22,000 years ago) sea level 395 feet lower than today This is when the sea bridge was exposed This is when the sea bridge was exposed 20,000 years ago the sea level was so low that the English Channel didn’t even exist.20,000 years ago the sea level was so low that the English Channel didn’t even exist.

Climate Through the Ages

Temps began to rise 14,000 years ago Temps began to rise 14,000 years ago Then temps sank again 12,700 years ago Then temps sank again 12,700 years ago This is known as the Younger-Dryas This is known as the Younger-Dryas

Climate Through the Ages Temps rose again to about 5,000 years ago (Holocene Maximum). Good for plants Temps rose again to about 5,000 years ago (Holocene Maximum). Good for plants

Climate During the Past 1000 Years At 1000, Europe was relatively warm. Vineyards flourished and Vikings settled Iceland and Greenland At 1000, Europe was relatively warm. Vineyards flourished and Vikings settled Iceland and Greenland

Climate During the Past 1000 Years From From Huge famines due to large variations in weather. Crops suffered. Huge famines due to large variations in weather. Crops suffered. Floods and great droughts Floods and great droughts

Climate During the Past 1000 Years From From Slight cooling causes glaciers to expand Slight cooling causes glaciers to expand Long winters, short summers. Vikings died Long winters, short summers. Vikings died Known as the Little Ice Age Known as the Little Ice Age

Climate During the Past 1000 Years Little Ice Age Little Ice Age 1816 – “Year Without A summer” 1816 – “Year Without A summer” Very cold summer followed by extremely cold winter Very cold summer followed by extremely cold winter

Temperature Trend During the Past 100-plus Years Warming from 1900 to 1945 Warming from 1900 to 1945 Cooling to 1960, then increasing to today Cooling to 1960, then increasing to today

Temperature Trend During the Past 100-plus Years Sources of temperature readings Sources of temperature readings Over land, over ocean, sea surface temps Over land, over ocean, sea surface temps Warming in 20 th century is 0.6°C Warming in 20 th century is 0.6°C Is global warming natural or manmade? Is global warming natural or manmade?

External Causes of Climate Change How can we change the climate? How can we change the climate? Emissions of CO 2 and other greenhouse gases are by no means the only way to change the climate.Emissions of CO 2 and other greenhouse gases are by no means the only way to change the climate. Changes in incoming solar radiation Changes in incoming solar radiation Changes in the composition of the atmosphere Changes in the composition of the atmosphere Changes in the earth’s surface Changes in the earth’s surface

Climate Change and Feedback Mechanisms Water vapor-greenhouse feedback Water vapor-greenhouse feedback Explain it (is it positive or negative?) Explain it (is it positive or negative?) Runaway greenhouse effect Runaway greenhouse effect Negative feedback mechanisms Negative feedback mechanisms Increase in temp…increase in radiant energy to space Increase in temp…increase in radiant energy to space What planet as a runaway greenhouse effect? What planet as a runaway greenhouse effect? Snow-albedo feedback (what kind is it?) Snow-albedo feedback (what kind is it?)

Climate Change, Plate Tectonics, and Mountain- building Theory of plate tectonics – moving of plates like boats on a lake Theory of plate tectonics – moving of plates like boats on a lake Evidence of plate tectonics Evidence of plate tectonics Glacial features in Africa near sea level Glacial features in Africa near sea level Fossils of tropical plants in high latitudes Fossils of tropical plants in high latitudes

Climate Change, Plate Tectonics, and Mountain- building Landmasses at high latitude create glaciers Landmasses at high latitude create glaciers Arrangements of landmasses disturb ocean currents Arrangements of landmasses disturb ocean currents Mountain building by plates running into each other Mountain building by plates running into each other

Climate Change and Variations in the Earth’s Orbit Milankovitch theory Milankovitch theory As Earth moves around the sun, three different movements affect solar radiation As Earth moves around the sun, three different movements affect solar radiation

Climate Change and Variations in the Earth’s Orbit Eccentricity Eccentricity Change in the shape of the orbit (from circular to elliptical Change in the shape of the orbit (from circular to elliptical Cycle is 100,000 years Cycle is 100,000 years More elliptical, More elliptical, more variation in solar radiation Presently in Low eccentricity

Climate Change and Variations in the Earth’s Orbit Obliquity Obliquity Change in the tilt of Earth’s axis Change in the tilt of Earth’s axis Cycle is 41,000 years Cycle is 41,000 years Smaller the tilt, the less seasonal Smaller the tilt, the less seasonalvariation Axis tilts from 22° to 24.5° Axis tilts from 22° to 24.5° What is our current tilt What is our current tilt

Climate Change and Variations in the Earth’s Orbit Procession Procession Wobble of the Earth as it spins Wobble of the Earth as it spins The Earth wobbles like a top The Earth wobbles like a top Currently, closest to the sun in Currently, closest to the sun inJanuary In 11,000 years, closest to the In 11,000 years, closest to the sun in July

Climate Change and Variations in the Earth’s Orbit

Climate Change and Atmospheric Particles Sulfate aerosols Sulfate aerosols Put into the atmosphere by sulfur fossil fuels and volcanoes Put into the atmosphere by sulfur fossil fuels and volcanoes Sulfate aerosols are thought to cool the climate and therefore counteract global warming to some extent.Sulfate aerosols are thought to cool the climate and therefore counteract global warming to some extent.

Climate Change and Atmospheric Particles Volcano aerosols Volcano aerosols May get into the stratosphere and absorb and reflect sunlight May get into the stratosphere and absorb and reflect sunlight Thus, warms the stratosphere and cools the troposphere Thus, warms the stratosphere and cools the troposphere

Climate Change and Atmospheric Particles Volcanic eruptions may be responsible for many of the climate’s cooling periods (Little Ice Age) Volcanic eruptions may be responsible for many of the climate’s cooling periods (Little Ice Age) Eruptions were larger 2.5 m.y.a and may be responsible for the Ice Age Eruptions were larger 2.5 m.y.a and may be responsible for the Ice Age

Climate Change and Variations in Solar Output Sunspots – magnetic storms on the sun that show up as dark region Sunspots – magnetic storms on the sun that show up as dark region Maximum sunspots, maximum emission (11 years) Maximum sunspots, maximum emission (11 years) Maunder minimum – 1645 to 1715 when few sunspots happened Maunder minimum – 1645 to 1715 when few sunspots happened

The Recent Warming Radiative forcing agents – greenhouse gases that can disturb the radiative equilibrium Radiative forcing agents – greenhouse gases that can disturb the radiative equilibrium Climate models are used to see the futureClimate models are used to see the future They use data from Carbon dioxide, other greenhouse gases, aerosols, and moreThey use data from Carbon dioxide, other greenhouse gases, aerosols, and more

Future Warming - Projections, Questions and Uncertainties Questions and uncertainties Questions and uncertainties How fast will Carbon dioxide increase? How fast will Carbon dioxide increase? Can we stop deforestation? Can we stop deforestation? Can we stop burning fossil fuels? Can we stop burning fossil fuels?

Future Warming - Projections, Questions and Uncertainties Uncertain effect of clouds Uncertain effect of clouds More clouds, more reflection to space? More clouds, more reflection to space? More clouds, more longwave radiation absorbed? More clouds, more longwave radiation absorbed?

Possible Consequences of Global Warming Projected temperatures Projected temperatures Temperatures will rise most in high latitudes Temperatures will rise most in high latitudes Expanding boreal forest will increase temps Expanding boreal forest will increase temps Plants and animals will die Plants and animals will die Precipitation will increase worldwide Precipitation will increase worldwide Possible effects on global circulation Possible effects on global circulation Weather shifts from normal pattern Weather shifts from normal pattern More rain than snow in the West More rain than snow in the West Rise in sea level Rise in sea level Melting glaciers Melting glaciers Contamination of groundwater Contamination of groundwater

Possible Consequences of Global Warming

Fig , p. 407

Global Warming and Human Impact on the Earth’s Surface Desertification – process of overgrazing and excessive cultivation of grasslands, causing desert conditions Desertification – process of overgrazing and excessive cultivation of grasslands, causing desert conditions An interesting theory An interesting theory Plagues could be nature’s way of “curing” the Earth of Global Warming Plagues could be nature’s way of “curing” the Earth of Global Warming Plagues kills us and our effects, allowing the Earth to heal (Gaia Hypothesis) Plagues kills us and our effects, allowing the Earth to heal (Gaia Hypothesis)

Curbing Global Warming Kyoto Protocol Kyoto Protocol A format agreement by hundreds of nations to curb greenhouse emissions A format agreement by hundreds of nations to curb greenhouse emissions Try to reduce emissions by 5% below 1990 levels by 2012 Try to reduce emissions by 5% below 1990 levels by 2012 Geoengineering Geoengineering Trying to fix the atmosphere with technology Trying to fix the atmosphere with technology Idea to put sulfate aerosols into atmosphere to cool it Idea to put sulfate aerosols into atmosphere to cool it