BIOL 3999: Issues in Biological Science

GLOBAL CHANGE BIOLOGY

Dr. Tyler EvansEmail: tyler.evans@csueastbay.eduPhone: 510-885-3475Office Hours: M,W 10:30-12:00 or by appointmentWebsite: http://evanslabcsueb.weebly.com/

PREVIOUS LECTURE• concentration of CO2 in atmosphere is

increasing (Keeling curve)• actually accelerating too

• CO2 is a greenhouse gas that contributes to the greenhouse effect• Earth retains heat from Sun

• CO2 will continue to increase in the near future• highest scenario most closely tracks

present-day trends

LINK BETWEEN CO2 AND TEMPERATUREEFFECT OF CO2 ON CLIMATE

• expectation is that increases in atmospheric CO2 will warm the planet• thus, necessary to establish correlation between CO2 and temperature• several ways scientists study how temperature and CO2 are changing

INSTRUMENTAL TEMPERATUREMEASUREMENTSSATELLITES PALEOCLIMATIC DATA

1. TEMPERATURE

• satellite measurements have been used to reconstruct global atmospheric temperatures since the 1970’s

• the satellite record is very short and hard to interpret due to changes in instruments and orbits

• despite these limitations, the latest satellite studies confirms the globe is warming.

SATELLITES

• the record of instrumental temperature measurements extends back to the 19th century• provides clear indication that the modern earth is warming• mean annual surface air temperatures of the earth have risen approximately 0.5°C (0.9°F)

since 1860.

INSTRUMENTAL TEMPERATURE MEASUREMENT

PALEOCLIMATIC DATA• beginning in the 1970's, paleoclimatologists began constructing a blueprint of how the

Earth's temperature changed over the centuries before 1850 and the widespread use of thermometers

• preserved physical characteristics of the past that stand in for direct measurements to enable scientists to reconstruct past climatic conditions

CLIMATE PROXIES

KEY CLIMATE PROXIES• many biological and geophysical processes are sensitive to variation in climate and

thus record in their structures information that may be used to reconstruct the climate at their time of formation

• sensitive to particular features of the climate system, such as temperature• limited to specific frequencies of time beyond which proxy is no longer accurate

• HISTORICAL RECORDS• CORALS• FOSSIL POLLEN• TREE RINGS• OCEAN LAKE SEDIMENTS• ICE CORES

HISTORICAL RECORDS• grape-harvest dates, which are tightly related to temperature, have been recorded locally

for centuries in many European countries.• early harvest dates reflect warmer summers, later harvest dates cooler summer these

dates may therefore provide one of the longest uninterrupted series of regional temperature anomalies (1370-present)

CORALS• corals build their hard skeletons from calcium

carbonate• carbonate contains isotopes of oxygen that can

be used to determine the temperature of the water in which the coral grew

• these temperature recordings can then be used to reconstruct climate during that period of time that the coral lived (up to 200 years for some corals)

http://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance/

18O isotope

FOSSIL POLLEN• each species and genus of plants produces pollen grains which have a distinct

shape• these shapes can be used to identify the type of plant from which they came• pollen grains preserved in the sediment layers of a pond, lake or ocean, can tell

us what kinds of plants were growing at the time the sediment was deposited

• the range of plant species are defined to certain climates. • the presence of pollen suggests that plant must have grown near by.

TREE RINGS (DENDRCHRONOLOGY)• tree growth is influenced by climatic conditions, patterns in tree-ring widths, density,

and isotopic composition reflect variations in climate• in temperate regions where there is a distinct growing season, trees generally

produce one ring a year, and thus record the climatic conditions of each year.

OCEAN AND LAKE SEDIMENTS• between 6 and 11 billion metric tons of sediment accumulate in the ocean and lake

basins each year.• sediments consist of materials that were produced in the lake/ocean or that washed

in from nearby land• tiny fossils and chemicals in the sediments can be used to interpret past climate• scientists drill cores of sediment from the basin floors to get an extended time course

• the presence or absence of certain species can be used to infer ocean conditions; most commonly temperature and salinity

ICE CORES• no source of paleoclimatic data has been as informative as ice cores taken from the

polar ice caps of Greenland and Antarctic• snow that falls does not melt and is incorporated in glacial ice. Therefore, deeper the ice

the further back in time that snow fell• this ice contains air bubbles trapped during freezing that contain CO2• ice cores can date back 650,000 years!

2. CARBON DIOXIDE (CO2)

HOW DOES CO2 CORRELATE WITH TEMPERATURE?

Temperature change (°C)

AtmosphericCO2 (ppm)

• CO2 increases, temperature increases

• ice-core data show, the increase in carbon dioxide is unprecedented and well outside the range of natural variations. The recent increase matches the increase calculated from the fossil fuel emissions.

ALL THESE DIFFERENT SOURCES OF DATA TELL A REMARKABLY CONSISTENT STORY

Temperature change (°C)

AtmosphericCO2 (ppm)

2013(390 ppm)

NATURAL VARIATION DOES NOT ACCOUNT FOR WARMING THAT HAD OCCURRED

• small changes in Earth’s orbit, angle amount of Sun’s energy reaching the surface

• models that only consider natural forces do not explain recent warming

INDICATORS OF GLOBAL WARMING

WARMEST YEAR ON RECORD?

GLOBAL WARMING-refers to the recent and ongoing rise in global average temperature near Earth's surface. Global warming is causing climate patterns to change. However, global warming itself represents only one aspect of climate change.

CLIMATE CHANGE-refers to any significant change in the measures of climate lasting for an extended period of time. In other words, climate change includes major changes in temperature, precipitation, or wind patterns, among other effects, that occur over several decades or longer.

Global mean 1901-2009

A CENTURY OF WARMING WORLD-WIDE

• change in average temperature world-wide since 1901

A CENTURY OF WARMING IN THE U.S.• average air temperatures change in different parts of the United States since the

early 20th century • since 1901 for the lower 48 states, 1905 for Hawaii, and 1918 for Alaska

• percentage of the land area of the lower 48 states with summer daily low temperatures well above normal is increasing

LOW TEMPERATURES AREN’T AS LOW AS THEY USED TO BE

• distinguished by a rise in extremely high nighttime temperatures

DROUGHT: 30-60% OF U.S. AT ANY GIVEN TIME• data from the U.S. Drought Monitor are only available for the most recent decade,

there is no clear long-term trend in this indicator• over the period from 2000 through 2009, roughly 30 to 60 percent of the U.S. land

area experienced drought conditions at any given time

U.S. LANDS UNDER DROUGHT CONDITIONS (2000-2009)

OCEANS ALSO GETTING WARMER

OCEAN HEAT CONTENT (1955-2008)

• however, changes in ocean heat content have important consequences on ocean processes such as circulation patterns and currents

• in three different data interpretations, the long-term trend shows that ocean heat content has increased substantially since 1955

• when sunlight reaches the Earth's surface, the world's oceans absorb some of this energy and store it as heat.

• If not for the large heat storage capacity provided by the oceans, the atmosphere would grow warmer at a much faster rate

OCEANS ALSO GETTING WARMER• average surface temperature of the world's oceans has increased from 1880-2009 from

1901 through 2009, temperatures rose at an average rate of 0.12 degrees per decade. • over the last 30 years, sea surface temperatures have risen more quickly at a rate of 0.21

degrees per decade• sea surface temperatures have been higher during the past three decades than at any

other time since 1880

AVERAGE GLOBAL SEA SURFACE TEMPERATURE 1880-2009

ICE IS MELTING:GLACIERS

• glaciers respond to warming by thinning and retreating up-valley to higher altitudes.

• a shrinking glacier thins faster near the terminus (the lowest part of the glacier) than near the head (the highest part of the glacier), which is why the terminus retreats up-valley while the glacier head remains in place

ICE IS MELTING: EXTENT OF ARCTIC SEA ICE

• extent of sea ice cover in the Arctic has been decreasing since 1975

• the lowest sea ice extent on record occurred in September 2007, which was 490,000 square miles smaller than previous minimum

• Approximately 1 million square miles than the average extent from 1975-2000

SEPTEMBER AVERAGE ARCTIC SEA ICE COVERAGE

ICE IS MELTING: EXTENT OF ARCTIC SEA ICESEPTEMBER AVERAGE ARCTIC SEA ICE COVERAGE

LESS SNOWFALLTRENDS IN APRIL SNOWPACK FOR WESTERN U.S.

1950-2000

REDUCED SNOWFALL

INCREASED SNOWFALL

• from 1950 to 2000, April snow water equivalent declined at most of the measurement sites with some relative losses exceeding 75%

LESS ICE AND SNOW CREATES A POSITIVE CLIMATE FEEDBACK LOOP

• a feedback is when an initial process triggers changes in a second process that in turn influences the initial process.

• a positive climate feedback increases the climate warming, while a negative climate feedback decreases that warming.

• the dark ocean surface absorbs most of the Sun's energy, while sea ice reflects most of it. • as the air and ocean warm sea ice melts. As ice melts, more of the dark ocean surface is

exposed. • the exposed ocean surface absorbs more of the Sun's energy, leading to greater melting of

sea ice.

LESS ICE AND SNOW CREATES A POSITIVE CLIMATE FEEDBACK LOOP

LECTURE SUMMARY• atmospheric concentration of CO2 and temperature are very tightly

correlated. • as CO2 increases so to do temperature

• multiple lines of evidence prevent a very consistent story: climate is warming at an unprecedented rate

• direct temperature measurements• paleoclimatology-historical records, corals, tree rings, fossils• ice cores provided the longest and most important temperature and

CO2 record• natural variation cannot account for all of the change that has

occurred• sea surface temperature and ocean heat content are increasing• glaciers and ice are melting-forms a positive feedback loop

MORE INFORMATION

United States Geological Surveyhttp://pubs.usgs.gov/fs/2009/3046/

PALEOCLIMATOLOGY

GLACIERS AND WARMING

http://www.ncdc.noaa.gov/paleo/globalwarming/index.htmlNOAA National Climatic Data Center-Paleoclimatology

INDICATORS OF CLIMATE CHANGE

http://www.epa.gov/climatechange/science/indicators/index.html Environmental Protection Agency

NEXT LECTURE:BIOLOGICAL EFFECTS OF TEMPERATURE