CLIMATE CHANGE FINAL PT 2
What effect could sulfate aerosols be having on global climate? What is the implication of this effect on the pace of greenhouse gas warming?
Aerosols reflect and absorb radiation from the sun. causing climate to cool, a reduction in aerosols in order to improve air quality, could lead to an extra warming of climate. Aerosols have also been proposed as a means of mitigating greenhouse gas warming (geo-engineering), either by using them near the Earth's surface to make extra clouds, or by injecting them into the stratosphere to reflect the sun's radiation to space. Aerosols, coated/mixed with dust particularly black carbon, can alter reflectivity by depositing a layer of dark residue on ice and other bright surfaces. In the Arctic especially, aerosols from wildfires and industrial pollution are likely hastening the melting of ice. can indirectly change climate via clouds causing cooling can affect weather patterns and reduce rainfall affect health The major influence of volcanoes is to inject sulfur dioxide into stratosphere where it combines with water to form sulfate aerosols (suspended fine particles or droplets). They linger there for months or years, reflecting sunlight and cooling Earth's surface. As can be seen from the graph on the upper right, the usual pattern is for several years of cooler temperatures following a major eruption, followed by increasing temperatures. This patterns is not consistent with the strong upward trend in global temperatures that has been observed in recent decades (lower right). Climate models incorporate data from volcanic eruptions quite well, as indicated by the close relationship between model predictions and observed surface temperatures in the graph at lower left.
What are some of the physical processes that we monitor to understand the direction and pace of anthropogenic climate change? What are some of the biological indicators? Give examples of both.
Geophysical: Ice extent, ocean warming Biophysical: Coral bleaching, bark beetle spread, vegetation mix/extent
What methods do we use to predict the future of anthropogenic climate change? What limitations do these methods have?
Global Climate Models. GCMs are mathematical formulations of the processes that comprise the climate system, including radiation, energy transfer by winds, cloud formation, evaporation and precipitation of water, and transport of heat by ocean currents. A disadvantage of climate models is that, although computer power continues to increase rapidly, global models currently do not resolve features smaller than about 50 miles x 50 miles. This makes it impossible to resolve smaller-scale climate features
What is the Holocene Thermal Maximum? What caused it? Why isn't it at the same time as the Early Holocene Insolation Maximum?***
Holocene Thermal Maximum: 6,000 years ago. Evidence of the warming caused by the increase of the early Holocene insolation. Pollen was proxy. Early Holocene Insolation Maximum: 8-10,000 years ago. Caused by where we were in the precession of the equinoxes. 8% more insulation in the summer. a warm period during roughly the interval 9,000 to 5,000 years BP, with a thermal maximum around 8000 years BP. what caused it: The effect would have had maximum Northern Hemisphere heating 9,000 years ago, when the axial tilt was 24° and the nearest approach to the Sun (perihelion) was during the Northern Hemisphere's summer. The climatic event was probably a result of predictable changes in the Earth's orbit (Milankovitch cycles) and a continuation of changes that caused the end of the last glacial period.
Can we count on natural climate change to negate the effects of human activities? Why or why not?
Not entirely. Unprecedented amounts of carbon. humans responsible for majority of carbon budget
Was the Little Ice Age a local, regional, or global event? Describe some evidence that supports this view? What factors may have caused it?
Regional to Europe and North America. Glaciers in the alps, reports of harsh winters. Volcanic eruptions- releasing sulphur dioxide into the atmosphere reducing solar radiation coming in. Variations in solar energy- Sunspots were less frequent during the LIA. More reflectivity of the earths surface- lower temperatures would've produced more snow and ice that reflect sun light away.
Why is the arctic responding so dramatically to greenhouse warming? Why is the Antarctic not responding in the exact same fashion?
The Arctic - has a lack of land makes it more susceptible to ocean currants - undergoes massive summer melts, the ocean absorbs more of the sun's energy, causing the ocean water to further heat up Antarctica - strong winds swirling around the South Pole are responsible for the icy expansion. - The winds make the sea ice move faster, causing it to deform into thick ridges that are harder to melt - The bunching of the ice creates regions of thinner ice and open water. In winter, these areas lose heat from the water more easily, so more ice forms. In summer, the sun warms the water, but there is very little ice to melt. -The mighty Southern Ocean Circumpolar Current prevents warmer ocean water from reaching the Antarctic sea ice zone, helping to isolate the continent. The winds within that ice zone keep the water extremely cold, enabling the sea ice cover to grow in recent years even as global temperatures have risen markedly.
What was wrong with the glacial chronology developed from the relationships of terminal moraines in North America?
The timeline does not show all the events. Erasure effect. Not a complete record.
What factors will cause sea level rise in a greenhouse warmed world? What amount (relative) of sea level rise will result from each factor?
The two major causes of global sea level rise are 1.) thermal expansion caused by warming of the ocean (since water expands as it warms) 0.6 mm per year 2.) increased melting of land-based ice, such as glaciers and ice sheets. 1.8mm per year - The study estimates that extra meltwater caused sea levels to rise by about 1.8mm per year, three times more than thermal expansion, which caused about 0.6mm of sea level rise per year. - If all the ice covering Antarctica, Greenland, and in mountain glaciers around the world were to melt, sea level would rise about 70 meters (230 feet)
How might global dimming have caused the drought in Ethiopia in the 1980s?
caused the droughts in Ethiopia in the 1970s and 80s where millions died, because the northern hemisphere oceans were not warm enough to allow rain formation.
Be able to list and describe geosigns and biosigns of climate change
geosign: • Temperatures are rising world-wide due to greenhouse gases trapping more heat in the atmosphere. • Droughts are becoming longer and more extreme around the world. • Tropical storms becoming more severe due to warmer ocean water temperatures. • As temperatures rise there is less snowpack in mountain ranges and polar areas and the snow melts faster. • Overall, glaciers are melting at a faster rate. • Sea ice in the Arctic Ocean around the North Pole is melting faster with the warmer temperatures. • Permafrost is melting, releasing methane, a powerful greenhouse gas, into the atmosphere. • Sea levels are rising, threatening coastal communities and estuarine ecosystems. biosign: coral bleaching, bark beetles
Why is the northern hemisphere so important in understanding the Last Glacial Maximum?
majority of the ice glaciers were in the NH
How did the Laurentide Ice Sheet affect weather patterns in North America?
more moisture, precipitation, and expansion of lakes (Lake Bonneville)
Where do we get the best record of how many ice ages there have been?***
pollen
What is the difference between proglacial and pluvial lakes? Give an example of each.
proglacial: a short-lived lake that develops after the retreat of an ice sheet in the bedrock depression left by the weight of the ice (ex. Lake Agassiz pluvial: a body of water that accumulated in a basin because of a greater moisture availability resulting from changes in temperature and/or precipitation (ex. Lake Bonneville)
What is ice rafted debris? What can we learn from it?
sediments of widely ranging sizes eroded from the land by ice, carried to the ocean, and deposited on the seafloor Ice rafting may be used for analysis of ice drift pattern by matching the rafted sediment with its origin. Tells us ocean temperature by distance traveled.
What are the warming implications of global dimming?***
since global dimming reflects solar dimming, that if it were to be solved, it would potentially raise temperatures even more hiding the true power of global warming: "By cleaning up global dimming-causing pollutants without tackling greenhouse gas emissions, rapid warming has been observed, and various human health and ecological disasters have resulted, as witnessed during the European heat wave in 2003, which saw thousands of people die."
Describe the trends in average global temperature over: 1) the past 1000 yrs., 2) the past 140 yrs. How well do model outputs match with these data?***
temperature trends past 1000 yrs 11th-14th centuries relatively warm period 15th-19th centuries little ice age - no sun spots in the 1600s 20th century warmest period within this time frame. This increase in average temperature appears to be the largest increase in temperature of any century during the past 1,000 years Temperature trends past 100-plus years -The warming has not been uniform over the globe -greatest warming occurs in the Arctic -Parts of the Southern Ocean Antarctica have not seen warming -The US has experienced less warming -Most of the warming has occurred at night
What/ when/how long/ how rapid/ where were effects felt of the Younger Dryas? What is hypothesized to have caused it? What evidence has been found to support these hypotheses?** pg 279-280
what: resulted in a decline of 2 to 6 degrees Celsius (3.6 to 10.8 degrees Fahrenheit) and advances of glaciers and drier conditions, over much of the temperate northern hemisphere. It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh cold water from North America to the Atlantic. What Caused Younger Dryas: 2 hypotheses. 1.) Change in ocean currents involving fresh water input from melting ice obstructing flow of warm saline water. evidence: negative delta 0-18 signal in sediments from gulf of mexico 2.)Or meteorite impact that darkened sky and cooled planet.
What is isostatic rebound and what does this have to do with deglaciation?
(also called continental rebound, post-glacial rebound or isostatic adjustment) is the rise of land masses that were depressed by the huge weight of ice sheets during the last ice age The melting of glaciers after the end of the ice age has caused the crust they were sitting on to rebound upward.
Why should we try to limit temperature increases below 1.5 degrees C? What are the feedbacks that might cause runaway greenhouse warming? https://climate.nasa.gov/news/2458/why-a-half-degree-temperature-rise-is-a-big-deal/
- Heat-wave duration, rainstorm intensity and sea-level rise would increase by roughly a third (and sea level is likely to continue rising long after air temperature is stabilized). - There would be a disproportionately greater impact on certain basic crops. Tropical coral reefs would be wiped out. The Mediterranean area's reduction in fresh water would double. - Tropical coral reefs would be wiped out. - The Mediterranean area's reduction in fresh water would double.
What was the cryogeography of the LGM? Where were the major ice sheets
- vast ice sheets 2km high or more covered much of North America, northern Europe, and Asia. - major ice sheets in NH were located in In North America: Laurenentide ice sheet in Canada, Cordilleran ice sheet in American West, Scandinavian ice sheet in northern europe, and Barents ice sheet on the northern continental shelf
What is the Early Holocene Insolation Maximum? What caused it?***
-The Holocene Climate Optimum (HCO) was a warm period during roughly the interval 9,000 to 5,000 years BP, with a thermal maximum around 8000 years BP -caused by orbital changes creating maximum Northern Hemisphere heating 9,000 years ago, when the axial tilt was 24° and the nearest approach to the Sun (perihelion) was during the Northern Hemisphere's summer.
What are the key uncertainties in predicting the pace and extent of global climate change due to human activities?
1) We don't know how much greenhouse gases (espcially CO2) will be emitted. 2)We don't know what the atmospheric levels will be due to the uncertainty of uptake processes by sinks 3) We don't know what the Earth's sensitivity and response to the higher levels will be
When discussing the "uncertainty" of the impacts of humans on future climate- what are "known unknowns?"
1. climate sensitivity- how climate is going to react to green house emission. 2.We also don't know how many emission we will have in the future. how water planning might have to respond to social unrest caused by long-term drought in the Southwest during the next 30 years for much longer term thinking about how humans could manage real disasters such as the complete destruction of Earth's habitability This is also true for climate change. It is certain that climate change is happening and driven by human factors. But its inherently complex nature makes it less clear what the impacts will be—including when and where they'll happen, or to what degree. The uncertainty of future climate policies, greenhouse gas emissions, complex climate and socioeconomic feedback loops, and unknown tipping points all further complicate our projections.
When talking about recent climate change, what 3 facts are indisputable?
1. greenhouse gases trap long-wave energy/heat in the Earth's atmosphere 2. concentrations of CO2, CH4 and other greenhouse gases have been accumulating in the atmosphere over the past 100 years at an increasing rate because of human activities 3. earth's average surface temperature has warmed by ~1 degree celsius in the last century
What are the relative abundances of CO2 and CH4 during: 1) glacial maxima, 2) interglacials previous the present one, 3) now.
1. ∼190 ppm CO2, 375 p.p.b.v CH4 2.~280 ppm CO2 at the beginning of the industrial age, 722 ppb CH4 3.) current concentration is ~400 ppm, 1800 ppb CH4
How have the magnitudes of climate oscillations changed since the end of the last glaciation? Give examples of 1) climate events and 2) temperature change.
1.) LGM was 21,500 years ago, 9.0°C 2.) Younger dryes (YD) 11-12,000 years ago, 8-10 degrees celsius cooler . 3.) Medieval warm period. (MWP) (900-1300 AD)- 2°F (1°C) warmer 4.) LIA between 1300 and 1870AD, 1.0 celsius degrees cooler.
What is the range of average global temperature increase from model output? What factors that we cannot know about affect the range of these results?***
3-5 degree celsius rise the implementation of new technologies and renewable energy and other actions to mitigate