Foreword • The issue of global climate change may be one of the most important issues facing humanity in its history • This issue has the potential to affect the economies, safety and health of the entire world’s population • Hopefully you’ll understand after this review why the science of this topic is so difficult to understand and why it generates so much political controversy
The Earth Systems Science Approach recognizes four natural subsystems: atmosphere, hydrosphere, geosphere and biosphere. Most researchers now recognize a fifth, non-natural subsystem: the anthroposphere. The Earth’s climate system consists of complex interactions between many components!
Global Climate Change • We’ll focus on some basics of the climate system such as atmospheric chemistry and the greenhouse effect • While examining the probable way human actions may be modifying climate and contributing to global warming, we’ll also recognize that there are natural mechanisms of climate change (Remember our discussion of glacial-interglacial mechanisms?)
Greenhouse Effect • Greenhouse Effect - the gradual warming of the Earth’s atmosphere and surface resulting when heat radiated from the Earth’s surface is absorbed by certain atmospheric gases (e.g., water vapor, carbon dioxide, CO2, and methane, CH4) • The gases that absorb and reradiate the heat are called greenhouse gases; these gases exist in trace concentrations in the atmosphere (see slides)
Greenhouse Effect – gradual warming of the Earth’s lower atmosphere and surface when certain gases (e.g., H2O, CO2 and CH4 ) absorb heat radiated from the Earth’s surface About 30% of incoming solar energy reflected back to space Sun Greenhouse gases absorb radiated heat and reradiate some of it to the lower atmosphere radiated heat Earth materials and atmosphere absorb about 70% of incoming light energy; some portion of this energy is emitted to the atmosphere as radiated heat
Earth’s Atmospheric Composition (Dry Air)
Greenhouse Effect • Don’t use the terms “greenhouse effect”, “greenhouse warming” and “global warming” synonymously - they are related, but different topics • Would the average person view the greenhouse effect as beneficial or detrimental? • Most people erroneously think that the greenhouse effect is detrimental; the greenhouse effect is a natural phenomenon that helps modify the Earth’s climate and produce livable biological niches
Greenhouse Effect • Atmospheric scientists suggest the Earth’s average surface temperature would be about 60 - 70 degrees F colder without a greenhouse effect; under these conditions most of the Earth’s surface would host Arctic conditions - the flora and fauna of Earth would be drastically reduced in number and diversity
Greenhouse Effect • So: the greenhouse effect is a natural phenomenon; “global warming” indicates that average global temperatures are rising but implies no particular cause(s); “greenhouse warming” indicates that average temperatures are rising due to increased concentrations of atmospheric greenhouse gases
Global Warming Evidence • There is firm evidence that the greenhouse effect is being enhanced and that we are entering a global warming period • This evidence includes: • 29 of the highest world average annual temperatures ever recorded (since 1880) recorded from 1976-2013; with the exception of 1998, the nine hottest years have occurred since 2001 (2013 was the fourth hottest global year on record, 2005 and 2010 the hottest); • about a 50% reduction in European Alps glacier ice in the last 100 years; Source: National Geographic, Sept. 2012
Global Warming Evidence an average rise in world sea levels of about 1 foot during the last century; a decline of about 42% in Arctic sea ice volume in the last 30 years; and the quick melting of portions of the Greenland and Antarctic ice sheets and Antarctic ice shelves (1995, 2002 and 2008 – in March 2002 a portion of the Larsen ice shelf the size of Rhode Island (1250 mi2 ) collapsed into the Antarctic Ocean) (see slides) Change in Arctic Sea Ice Minimum 1979-2007
Global Warming • The accumulating evidence suggests global warming is occurring but whether natural or human forces (or both) were causing climate change was vigorously debated • However, the debate in the scientific community has mostly ceased • Why? See slides
Global Climate Research • The IPCC (Intergovernmental Panel on Climate Change – consisting of more than 1500 scientists from about 60 nations) released a paper in February 2001 contending the evidence was significant to support that human actions are modifying the climate • Furthermore: a November, 2004 report published by 250 scientists from eight nations indicates that the Arctic is warming twice as fast as the rest of the globe – in their opinion likely the consequence of increased atmospheric levels of greenhouse gases due to increased fossil fuel combustion by humans
Global Climate Research • In February, 2007 the IPCC issued their next report. They contend that the rise of global temperatures since the mid-1900s is very likely (90% certainty) the product of the release of fossil fuel combustion gases • However, note the partial scan of the following recent newspaper article that suggests a similar warming trend occurred naturally during the last millennium
Global Climate Change • The 2013 IPCC (Intergovernmental Panel on Climate Change) report contends that human actions are significantly driving climate change (95% confidence level)
Global Climate Research • In simple models, the more greenhouse gases in the atmosphere the more radiated heat from the surface gets trapped and the higher the atmospheric and surface temperatures • What are some natural sources of greenhouse gases?
Greenhouse Gas Sources • What are some other natural sources of greenhouse gases? Are these sources easy to accurately quantify on a worldwide basis? • Is this a simple or complex research topic?
Global Climate Research • How can we discern with 100% certainty whether humans are the primary cause of any global warming that’s occurring?
Climate Reconstruction Research • Ice sheet core samples (see figure) and other materials are being ingeniously investigated for their ability to retain indications of prior atmospheric chemistry and temperature • Scientists are attempting to detail ancient atmosphere greenhouse gas levels to see if they’ve ever fluctuated as much naturally as they’ve done in the last 55 years
Climate Reconstruction Research • Particularly, scientists are interested in establishing how pre- and post-Industrial Revolution atmospheric greenhouse gases have fluctuated • Why is this research important? Why should you care?
Global Climate Research • Although evidence supports that circa 1840 air CO2 levels were about 270 ppm (parts per million) and that measured air CO2 levels from 1958 to present have risen from about 310 ppm to about 400 ppm, we still can’t discern what percentage factor human activities are to atmospheric chemistry and climate changes
Global Warming • Why the uncertainty? Although reconstruction of ancient atmospheric chemistries and climates suggest that air CO2 levels haven’t been higher than currently in the last 650,000 years, the same data suggest CO2 levels have naturally fluctuated much more than within the last 160 years (millions of years ago). (see figure)
Global Climate Research • These same studies do support that higher atmospheric CO2 levels are associated with warmer climates • In addition, we are still learning about other sources of greenhouse gases and can’t be sure that we’ve quantified their releases accurately (see figure)
Possible Global Climate Change Outcomes • If atmospheric greenhouse gas concentrations continue to rise and enhance the greenhouse effect, what are some of the proposed consequences of global warming? • Remember: although the topic discussed is often called “global warming” the entire globe won’t be affected similarly, subsequently many researchers and politicians now employ the phrase, “global climate change”
Possible Global Climate Change Outcomes • Consequences could include: 1) significant rises in sea levels as increased glacial ice melting occurs; the rising waters could permanently displace millions of people (see figures); National Geographic: August, 2007
Possible Global Climate Change Outcomes • Note the adjacent example of the threat of rising seas • 2) Reduction of tillable land as sea levels rise;
Possible Global Climate Change Outcomes • 3) Changes in world weather patterns and a higher frequency of severe weather events (e.g., hurricanes, severe thunderstorms, blizzards, extended heat waves, droughts); North Atlantic Tropical Storm Frequency National Geographic: August, 2007
Possible Global Climate Change Outcomes Source: National Geographic, Sept. 2012
1980 - 1995: 46 US weather disasters with at least $1 billion in damages 1996 - 2011: 87 US weather disasters with at least $1 billion in damages Source: US National Climatic Data Center 2012 Superstorm Sandy
Possible Global Climate Change Outcomes • 4) A greater percentage of land becomes arid and less productive; the glacial source of some major rivers (e.g., the Ganges) may be reduced or eliminated long term (a few hundred years)
Possible Global Climate Change Outcomes CNN.com 3/31/06 • 5) The biodiversity of coastal ecosystems declines due to an inability to adapt quickly to rising, warming and acidifying seas (e.g., reefs); Bleached coral
Possible Global Climate Change Outcomes 1/26/2012 6) Diseases spread by flies, mosquitoes, ticks become more prevalent as the warmer climates produce longer and more intense infection periods (think about the rapid spread of West Nile Virus across the U.S.); and
7) The deep-water return flow of the Gulf Stream current is reduced/eliminated leading to much colder conditions in the North Atlantic (see figure) Warm, less salty surface current Gulf Stream: 50-90 miles wide; maximum discharge: 540 billion tons/hour Cold, salty deep current
Possible Global Climate Change Outcomes • Most climate scientists think there is enough evidence of these effects occurring to strongly support that global climate change is occurring at a rate that requires worldwide action • Complicating factors: How would climate change influence the Jet Stream or weather patterns generated during El Nino and La Nina events?
Possible Global Climate Change Outcomes • Please remember that the seven categories of global climate change outcomes we discussed are projections, not a guaranteed reality - the projections are based on incomplete data and an incomplete mathematical understanding of the Earth’s dynamic processes • The first global warming computer models treated the Earth as a rocky ball devoid of life - simpler to model mathematically!
Variables Affecting the Degree of Climate Change • There are other variables (factors) which may affect the degree of climate change. • 1) A few scientists have proposed that as air CO2 levels rise, plant productivity will rise since CO2 is necessary for photosynthesis; the more CO2 absorbed by plants the less likely a severe global warming event
Variables Affecting the Degree of Climate Change • Experiments with plants in CO2-enriched lab atmospheres and outside forest plots have produced variable results - hardwood trees respond positively and absorb more CO2 for a few years; most grasses and ferns show declines in productivity • Therefore could the distribution, and type, of plant species (and animals) across the globe be altered? (see figure)
Source: National Geographic, June, 2008
Variables Affecting the Degree of Climate Change • A nutrient (iron) seeding project in a portion of the southern Pacific ocean in 1993 successfully increased the population of CO2-absorbing phytoplankton, however the positive results were short-lived • Do you advocate “geoengineering” on a large scale? (see slide) • A Californian company, Climos, wants to commercialize iron fertilization and an India/Germany iron fertilization experiment was completed in 2009