Earth as a Living Planet - Climate Change

Climate

Describes average weather conditions over a long period of time for a particular region of Earth

Global Climate

Describes the average weather conditions over a significant period of time for the planet as a while

Temperature Records

• Weather stations began recording temperature records in 1714

• Weather satellites have added a level of sophistication with infrared radiation to record temperature in various layers of the atmosphere

• Lots of error historically

• Comparing temps to a fixed base period shows how much the climate is changing over time

Instrumental Period

Current era in which we have access to temperature reasings taken directly with instruments such as thermometers

Proxy

Observable and measurable phenomenon that serves as an indirect indicator of changes in climate (tree rings and coral skeletons can be used as proxies, showing records of changes in surface and seawater temperatures from the past)

Paleoclimates

• Ancient climate conditions understood through use of proxies

• Examining the ratio of heavier to lighter O2 in the air bubbles in ice cores from glaciers can tell us how cool past temperatures were in the last 700,000 years

• Heavier oxgen isoptops condenses faster than lighter oxygen isotope, and the colder the temperature is, the quicker the heavier isotope is depleted from the air

Climate has always changed

• Over geologic time, global climate has changed naturally

• Fossil evidence indivates that polar regions were forested during the Creataceous period

• 700-million-year-old glacial sediments near the equator suggest that Earth was completely iced over during the “snowball Earth” period

The Greenhouse Effect

• Some energy from the sun is trapped at the Earth’s surface, while some of this energy radiates back into space

• Happens in any system where a barrier causes an inflow of energy that outpaces the outflow such that the interior warms

• On Earth, the warming effect is due to atmosphereic greenhouse gases preventing radiant heat emitted from the surface escaping into space

• Earth is surrounded by greenhouse gases, redirect heat rising from Earth’s surface back down, causing a warming effects

• Light colored surfaces on Earth increase albedo, a measure of the reflectivity of a surface

• Darker surfaces absorb radiation and heat Earth’s surface

Continental Drift

• The positions of drifting continents relative to the equator affects the amount of solar radiation that reaches land to warm it, and movement of continents also influences ocean currents, which affects global heat distribution

• Colliding land masses create hills and mountains that affect climate by increasing land surface area exposure to natural acid in rain drops, which is created when CO2 dissolves in water droplets

• These rain drops remove CO2 from the atmosphere and store it in oceans and marine organisms

Composition of Biosphere

• Biosphere shapes climate over long time frames, ecosystems change the composition of the atmosphere by adding or using CO2 as part of the carbon cycle

Milankovich Cycles

• Regular patterns of variation in the shape of the Earth’s orbit, and the tilt and direction of Earth’s rotational axis

• These alter the amount of the Sun’s radiation and energy that reach Earth and its atmosphere

• The shape of Earth’s orbit changes in a 100,000 year cycle (eccentricity)

• The tilt (ubiquity) and direction (orbital procession) of Earth’s rotational axis changes every 26,000 to 40,000 years

• These cycles contribute to temp changes in the atmosphere and oceans, and long-term cycles can even affect ice ages

Eruptions and Asteroids

• Volcanic eruptions and asteroid stikes can have rapid effects on global climate change

• The 1883 eruption fo Krakota in Indonesia sent ash plumes nearly 50 feet up iin the air, reducing sunlight reaching the Earth, and cooling average global temperature by 1.1 C in that year

• The Permian-Triassic 252 million years ago is linked to volcanic activity in Siberia

Oceans

• Saltwater covers most of Earth and has a major impact on global climate

• The ocean is always moving as a connected flowing mass that transports energy around the globe, affecting areas thousands of miles from shore

• Gyres change temperatures, wind

Ocean Currents

• Rivers of the ocean

• Surface currents are ocean currents affecting the top 400 meters of ocean that starts from air blowing across the surface

• These travel in gyres, large circular ocean currents

• Gyres travel in circular patterns due to the Coriolis effect, a force driven by Earth’s rotation that deflects objects, winds, and currents on the surface of the Earth and in the ocean or atmosphere

• This causes gyres in the Northern Hemisphere to rotate clockwise, and those in the Southern Hemisphere to rotate counterclockwise

• Deep currents are the flow of water below the surface caused by variations in density, temp, and salinity

• Salinity is the concentration of salt in the water, generally measures in parts per thousand

• Both these factors contribute to the thermohaline conveyor, a large-scale ocean circulation driven by surface and deepwater ocean currents and changes in water temperature and salinity (density)

El Niño and La Niña

• Countercurrents or chnages in normal ocean currents, can happen and change weather

• The El Niño-Southern Oscillation is driven by jet stream changes

• Causes a countercurrent that significantly weakens or even shifts the direction of trade winds and ocean currents in the southern Pacific

• This affects upwelling currents, where cold water is drawn up from deep in the ocean

• Causes temporary sea level rises and rops, and has all sorts of impacts on weather, drought, floods, crop failure, ecosystem dieoff

Concentration of CO2 in the Atmosphere is Increasing

• Rate continues to increase

• Been measured for 60 years in the Mauna Loa Observatory, Hawaii (NOAA)

• Last time we saw concentrations this high was 1 million years ago

• Humans emit much more CO2 through fossil fuel combustion and industrial processes

Non-CO2 emissions

• Methane traps heat 25 times more effectively than CO2, stays in atmosphere 12 years (natural gas leaks, rice farming, livestock, landfills)

• N2O is 310 times more potent, lasts for 120 years (fossil fuel combustion, agriculture, wastewater treatment, nylon production)

Human-Cased Greenhouse Gases Affect Climate

• Troposphere has been warming with stratosphere cooling

• If planet was warming due to increasing solar radiation, the stratosphere would be warming along with the troposhere

• Hindcasting shows computer simulations in support of real-world observations, humans driving climate change, especially by releasing CO2 and methane

Precipitation and the Water Cycle

• Changes in precipitation patterns, frequency and intensity of extreme weather events are effects we are seeing due to climate change

• The Southwest and West have experienced droughts, increase heat waves have resulted in deaths

Sea-Level Rise

• Global sea levels have risen over 9 inches since late 19th century

• Thermal expansion

• Melting ice from land and glaciers

• Exacerbated by human actions like groundwater extraction or natural gas subsidence

Ecosystem Effects

• Increasing CO2 has also resulted in ocean acidification, ongoing decrease in pH of Earth’s oceans caused by absorption of CO2 from atmosphere

• Decrease in pH is equal to a 30% increase in acidity and interferes with calcium carbonate shell formations by many marine species, most of which are at the base of the marine food chain

• Phenology, the seasonal timing of biological activities, such as breeding, floweing, and migration of various species is changing

• Species are migrating towards the poles