Global Climate Change Earth is Warming How do we know? What do we know? How confident are hypotheses...

transcript

Global Climate Change

• Earth is Warming• How do we know?• What do we know?

• How confident are hypotheses about causes?• What are greenhouse gases?• Where do they come from, and how do we know?

• Most common claims of the skeptics• T’s are going down, not up• This warming is just part of a natural cycle• CO2 is good for plants

NOAA Global Historical Climatology Network: DATA

Stations with at least 10 years of record for these 30-yr intervals

http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/

The Historical T Data Network

From: Kitchen (2014) – Global Climate Change

Anomalies instead of Absolute T Data

1. Variations from station to station can be erratic due to small variations in local conditions

2. Regional anomalies are much more consistent, over a larger area, than station to station readings.

3. Anomalies allow more accurate assessment of T variation through time.

Days vs. Nights

IPCC - Data

IPCC - 2007

IPCC – Last 2000 yrs

IPCC- 2007

Land + Ocean T’s

National Research Council (2010) – weather stations + SST’s from direct and satellite measurements.

Melting Ice

http://visibleearth.nasa.gov/view.php?id=76590

Jakobshavn is the fastest-flowing glacier in the world. In 2010, the glacier moved at 15 kilometers per year, shedding ice into the Arctic Ocean as it surged from land to sea. It drains more than six percent of the Greenland ice cap and contributes more to global sea level rise than any other feature in the Northern Hemisphere. The glacier has both retreated and thinned in recent years. In 2010, Jakobshavnretreated 1.5 kilometers.

Greenland

http://earthobservatory.nasa.gov/IOTD/view.php?id=79369&src=ve

Antarctica

Two weeks after a new record was set in the Arctic Ocean for the least amount of sea ice coverage in the satellite record, the ice surrounding Antarctica reached its annual winter maximum—and set a record for a new high. Sea ice extended over 19.44 million square kilometers (7.51 million square miles) in 2012, according to the National Snow and Ice Data Center (NSIDC). The previous record of 19.39 million kilometers (7.49 million square miles) was set in 2006.

Arctic Sea Ice

Over the last decade, Arctic sea ice extents in September have set record lows three times, and the 2011 minimum nearly tied the 2007 record low.

National Snow and Ice Data Center (NSIDC)

“The nine lowest maximum extents have occurred in the last nine years, since 2004,” Meier says.

http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice.php

Warming + Melting = Sea Level Rise

Causes of Warming – How confident?

Visible light

Gamma rays

X raysShorter wavelengths and higher energy

Longer wavelengths and lower energy

UV radiation

Infrared radiation Microwaves TV, Radio waves

Wavelengths (not to scale)

0.001 0.01 0.1 1 10 0.1 10 100 0.1 1 10 1 10 100

Nanometers Micrometers Centimeters Meters

Electromagnetic Spectrum: light = energy = waves

Solar radiation

Reflected by atmosphere

Radiated by atmosphere as heatUV radiation

Lower Stratosphere (ozone layer)Most UV absorbed

by ozone Visible light Heat added to

troposphereTroposphere

Heat radiated by the earth

Greenhouse effect

Absorbed by the earth

Flow of Energy to and from the Earth

From: Miller (2010) Living in the Environment

What’s a Greenhouse Gas?

• Greenhouse gases respond to long-wave radiation (infrared radiation) by ‘vibrating’ – this vibration sends out (or re-radiates) a portion of that original infrared radiation – heat.

• Some of these are:• Water vapor• Carbon dioxide• Methane• CFCs• Ozone

Yellow = observed by satellites

Valleys = absorption by GHG’s

CO2 could raise overall heat budget of atmos. by 3%

National Research Council - GHG

Analysis of air bubbles trapped in Antarctic ice cores show that, along with carbon dioxide, atmospheric concentrations of methane (CH4) and nitrous oxide (N2O) were relatively constant until they started to rise in the Industrial era. Atmospheric concentration units indicate the number of molecules of the greenhouse gas per million molecules of air for carbon dioxide and nitrous oxide, and per billion molecules of air for methane. Source: U.S. Global Climate Research Prog.

How Do We Know We’re Adding CO2 to the

Atmosphere? 14C!• Living things incorporate 14C into their bodies in the

same proportion as it occurs in the atmosphere

• When the organism dies, it begins to lose 14C, via radioactive decay [half-life of 5730 yrs]

• Tree rings record relative amounts of 14C in the atmosphere, and show a large increase in the proportion of 12C since the industrial revolution

• This comes from fossil fuels, which are too old to have any 14C remaining

Fig. 3-19, p. 70

Carbon dioxide in atmosphere Respiration

Photosynthesis

Animals (consumers) Burning

fossil fuelsDiffusion Forest fires

Plants (producers)Deforestation

Transportation RespirationCarbon in

plants (producers)

Carbon dioxide dissolved in ocean

Carbon in animals

(consumers)Decomposition

Marine food webs Producers, consumers, decomposers

Carbon in fossil fuels

Carbon in limestone or dolomite sediments

Compaction

Process

Reservoir

Pathway affected by humans

Natural pathway

Carbon Cycle

Trends in CO2 : NOAA

http://www.esrl.noaa.gov/gmd/ccgg/trends/history.html

Temperature and CO2

Temperature change (blue) and carbon dioxide change (red) observed in ice core records Many other records are available

Temperature and CO2

An estimate from the tropical ocean, far from the influence of ice sheets, indicates that the tropical ocean may warm 5°C for a doubling of carbon dioxide. The paleo data provide a valuable independent check on the sensitivity of climate models, and the 5°C value is consistent with many of the current coupled climate models.

Temperature Projections - NOAA

http://www.climate.gov/#education/teachingResources

Global Climate Change Earth is Warming How do we know? What do we know? How confident are hypotheses...

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