ENVR - Global Climate Change Final

Climate Sensitivity for the future:

Sensitivity is more difficult to assess than one might think. Radiative forcing from greenhouse gases is relatively easy to assess. The feedback cycles initiated by this forcing are more difficult to quantify. One way to measure sensitivity is the equilibrium climate sensitivity. This is the equilibrium temperature rise (total amount of change after warming has stopped) for a doubled greenhouse effect. Also known as a 2xCO2 world.

False Challenges for data gathering of last 150 years:

Urban Heat island effect data fabrication - Climategate transparency Incorrect methods

What is one event that CAUSES a particular year to be warmer than usual?

a strong El Niño year

What is the best definition of an icehouse climate?

a world in which glaciers exist

What country has low historical emissions but high modern emissions (as a country)?

China

3 things needed to predict future climates:

Climate models Climate sensitivity Emission scenarios

True or False? Under ideal circumstances a carbon tax will be more economically efficient than a cap and trade program.

False.

Well - calibrated climate models in the future:

Generally, the climate models we have are good. They are able to recreate the general climate trends of the last 1,000 and 100 years. This includes temperature, precipitation etc. Climate models are not as good at simulating clouds (because they are small) and some medium-sized weather systems such as hurricanes (bigger, but very dynamic). Climate models are constantly improving.

Urban Heat Island Effect.

It is true that the ground surface in urban areas is less reflective and temperatures rise as a result. However several different analyses have shown that the overall temperature record is not distorted by this phenomenon. Mostly this is because urban areas represent only 1% of the world's surface (3% of land surface).

Compare and contrast mitigation and adaptation.

Mitigation: any action taken to prevent climate change from taking place, thereby preventing negative consequences. Adaptation: any action taken to avoid the negative consequences, but not to stop the climate changing. Pros of mitigation: reduces the amount of adaptation that everyone has to do, great for people without as much money (i.e. lower adaptive capacity). Keeps sea level lower & good for ecosystems who might have a harder time adapting to climate changes compared to humans. Pros of adaptation: easier to implement as it is defined response to a clear threat. The benefits of adaptation are also felt right away (near term benefits). The costs of each are going to be variable depending on many different factors.

Why do climate models succeed at looking far into the future where weather models fail?

Multiple simulations are averaged to eliminate the chaos of weather; climate models are not trying to figure out exactly what will happen on one exact day, they are trying to determine what that decade will be like; climate models look at long-term weather trends rather than the passage of individual weather systems

Emission Scenarios

Natural systems can absorb about 4 Pg (Gt) of carbon per year. Any emission value above this results in an increasing CO2 concentration in the atmosphere. If emissions fall from 10 to 9 Pg(C) per year, then the amount of CO2 in the atmosphere will still go up. If emissions fall from 4 to 3 Pg(C) per year, then the amount of CO2 in the atmosphere will fall.

Of the three emission scenarios that were discussed in detail, which leads to a stable (i.e. not increasing or decreasing) amount of CO2 in the atmosphere by the year 2100?

RCP 4.5

Impacts of Climate Change:

Precipitation changes will impact water supplies, agriculture, and flooding. Changes in the oceans will exacerbate ongoing issues related to fisheries. Sea level rise will cause coastal flooding and shoreline erosion. Crop productivity is expected to decline, especially for wheat and corn. Increased mortality from diseases and extreme heat waves. Some areas may become uninhabitable creating environmental refugees. Increased heavy precipitation events will lead to increased flooding along rivers in the affected areas. Adaptation includes flood control measures and relocation of infrastructure located within flood zones. Drier soils due to the warming-related increases in evaporation and transpiration, at least for places that do not see a commensurate increase in precipitation. Increased drought severity in places that experience declines in precipitation. Irrigation of farm land will be possible in places where a suitable water source exists. Warmer and more acidic oceans will exacerbate all of the non-climate related stresses currently affecting marine ecosystems and fisheries. Reduction of non-climate stresses (e.g., pollution, fertilizer runoff, overfishing, etc.) would help boost ecosystem vitality. Sea level rise will increase the risks associated with coastal flooding and shoreline erosion. Sea walls and other structures can be built around high-value coastlines, but not all areas could be protected Many crops are not particularly heat tolerant. Just a few hot days at the wrong time of the growing season can have outsized impacts on yields, especially for wheat and corn. Drier soils and outright drought conditions could also lead to decreased crop yields. Creation of heat and/or drought resistant crop varieties could help. This may require some amount of genetic modification of crop species. Heat waves lead to increased mortality, especially for outdoor workers, the elderly, the young, and the sick. Cooling centers and other community supports can help reduce this mortality. Changing precipitation and temperature patterns are affecting the distribution of some water-borne and vector-borne diseases. Improved water treatment facilities will help counter the spread of water-born illnesses. Vaccines under development may help combat the spread of diseases like malaria and dengue. Many people will be displaced by climate change-related issues like coastal and river flooding, persistent drought, etc. Refugee relocation programs will be needed to find new homes for what might be millions of people.

Why has Earth experienced periodic ice ages (as opposed to the current interglacial climate) over the last several hundred thousand years?

The ice ages are caused by periodic changes in Earth's orbit that lead to a prolonged period with cooler than usual summers -- a period of low eccentricity, low tilt and summer aphelion -- all cause a long period with cool summers. This is going to cause several different feedback processes to start: Temperature-albedo feedback Ice elevation feedback CO2 drawdown by increased solubility, changes in ocean chemistry, and fertilization from dust Water vapor feedback A drier planet will lead to increased prevalence of grasslands and more dust in the atmosphere, both of which cause increased reflectivity.

So far there is no energy silver bullet (that is to say that there is no simple way to moving away from fossil fuels). Aside from cost, explain the technological limitations of using alternative energy as opposed to fossil fuels.

There are two issues: Scalability: we have not been able to install enough wind and solar power to put a huge dent in our fossil fuel consumption, they have only fallen a few percent overall. Intermittency: a huge issue for both wind and solar is that they do not produce all the time and not necessarily when we need it. This means that surplus power will need to be stored and used later or transmitted long distances from places where the sun is still shining to places where it is not. This seems to be technologically difficult and financially expensive.

Climate scientists are now nearly completely convinced that the warming of the last several decades is primarily related to human activity, why?

There is 150 years of science to explain what greenhouse gases do in the atmosphere. We know that there are more of them in the atmosphere and that they should be causing warming. Climate models indicate that the amount of warming that we have seen is what's expected based on the observed increases in GHGs in the atmosphere. There are no known natural explanations for the amount of warming that has occurred.

Why are scientists uncertain about the amount of warming that will occur in the future for any given amount of greenhouse gas emissions?

They are uncertain of the amount and types of clouds that will form in the future. We know that there will be increased evaporation in a warmer planet and some will stay as water vapor, but some of it will condense to form clouds. It is hard for climate models to predict how many clouds will exist in the future, and if they will have a predominantly cooling impact by increasing reflectivity, or whether they will cause warming by trapping heat.

Something forces a change in a system that has a positive feedback process. By itself the forcing would have caused a 1°C cooling. What is the final result when the feedback is also considered?

a 1.5°C cooling

What best describes the usual conditions in the atmosphere over the equator?

because of the intense sun shine, the air near the ground surface is warmed and rises through the atmosphere

What is a true statement about changes in Earth's reflectivity over the last 250 years?

clearing forests to plant crops makes Earth's land surface more reflective

What is the fundamental requirement for a glacier to exist within a region?

cool summers so that some of a winter's snowfall survives summer melting and persists into the next winter

***What kind of driving/vehicle is best suited to reap the benefits of regenerative braking/hybrid technology?

garbage trucks

What best describes changes in solar behavior over the last 250 years (since 1750)?

generally speaking, the Sun has become a little bit more active

Which location is expected to experience the least amount of warming over the next several decades?

over the tropical Atlantic Ocean.

Geologists can estimate past air temperatures from measuring ___________ in glacial ice?

oxygen isotopes

What is the likely range and best estimate for climate sensitivity?

range = 1.5 to 4.5°C; best estimate = 2.5 to 3°C

What is a real challenge that makes the determination of Earth's average temperature over the last 100 years difficult, but not impossible?

some adjustments have to account for the fact that occasionally land use around the climate stations has affected their microclimates or changed the times of day when measurements were taken

Which of the following best describes changes in solar brightness over the last 40 years (since 1976)?

the Sun has gone through slightly brighter and dimmer phases, but there has been no overall change

What is expected in coming decades for places that are already reasonably wet?

the amount of rainfall will increase

Which part of Earth has absorbed most of the extra energy that is being trapped in our climate system?

the oceans

What country has a low carbon intensity?

United States

***What best describes the situation of people living on large river deltas?

-there will be increased flooding due to sea level rise -there may be increased flooding due to changes in river flow

3 Factors that might be controlling the warming of the planet and other changes:

1. Solar Activity 2. Albedo 3. Greenhouse Gases

In order to predict how climate will change over the next 100 years we need 3 things:

1. Well-calibrated climate models. 2. Knowledge of Earth's climate sensitivity to greenhouse strength. 3. Estimate of the concentration of greenhouse gases and sulfur pollutants in 2020, 2050, etc.

Which of the following locations is most likely to experience increased flooding in the future?

Boston, MA (woooooo!)

Compare and contrast the carbon tax and a cap-and-trade program.

Carbon tax: a cost is imposed on emissions. This will make fossil fuels more expensive and less attractive. Everyone has an incentive to conserve, but might be less economically efficient than a cap and trade program. The tax rate can be specified years in advance, which makes long-term planning useful. Cap and trade: an emission cap is set at a desired level (less than current emissions) and permits are distributed. There are not enough permits, so someone is going to have to reduce their emissions, which then enables them sell any excess permits to someone who did not reduce their emissions. Has potential to be more economically efficient, but also has more potential for exemptions, special rules etc., which will decrease the efficiency of the system.

Expected Climate Changes in the Future:

Changes in the Hydrosphere: The places most likely to see an increase in precipitation are the high latitudes, the equatorial Pacific Ocean, and the wet mid-latitudes. The places most likely to see a decrease in precipitation are the dry mid-latitudes, sub tropical regions. Further increases in the frequency of heavy precipitation events over most of the mid-latitude land masses. Changes in Cryosphere: nearly all glaciers will shrink substantially. -exception is parts of Antarctica where temps are so cold that temperatures will still be well below freezing. There will also likely be an increase in snowfall. Dramatic decreases in Arctic Ocean sea ice. Perhaps a nearly ice-free Arctic Ocean in RCP8.5 at the end of this century. Northern Hemisphere snow cover will decrease. Changes in Sea Level: IPCC estimates for sea level rise by 2081-2100: RCP2.6 26 to 55 cm RCP8.5 45 to 83 cm Sea level continues to rise for many decades after 2100 in all scenarios. under RCP2.6: temps peak in 2050.

What are Representative Concentration Pathways (RCPs) ?

Emission scenarios use the amount of emissions per year to determine the amount of CO2 in the atmosphere, and from that the amount of radiative forcing in W/m2. RCPs are identified by their total radiative forcing (W/m2) in the year 2100 relative to 1750. They span a range of possibilities from intensive effort to curb emissions to little action taken. They Include land use change and air pollution. Volcanoes erupt at random in these simulations based on historical trends.

Current Estimates of Climate Sensitivity:

Greenhouse gases themselves will cause 0.9°C warming for 2xCO2, but this is before the feedback processes. The equilibrium climate sensitivity is likely to be in the range 1.5 - 4.5°C. Best estimates are 2.5 - 3.0°C It is extremely unlikely to be less than 1°C; and very unlikely to be more than 6°C. The range of estimates is due to genuine scientific uncertainties about feedback systems.

Describe Earth's energy balance in terms of incoming and outgoing energy. How has this energy balance changed over the last 250 years?

Incoming = short wave from sun. Most absorbed at ground surface, some UV absorbed in atmosphere, some reflected off of clouds and ground surface Outgoing = thermal IR from Earth's surface. Most absorbed by GHGs in the atmosphere, only a small amount passes through atmospheric window. There has been a very slight increase in solar activity: +0.5 W/m2, there has been a medium increase in reflectivity: -0.97W/m2 and a large increase in the greenhouse strength: +3.18 W/m2.

RCPs

RCP 2.6 -Intensive mitigation efforts- warming: +1.0C RCP 4.5 - Stabilization in 2100 - warming: +1.8C RCP 6.0 - Stabilization after 2100 - warming: +2.2C RCP 8.5 - Very high emissions - warming: +3.7C Temperatures continue to rise after the year 2100 in all scenarios except RCP2.6.

Of the three emission scenarios that we discussed in detail, which leads to the most emissions?

RCP 8.5

Explain why Earth's climate has remained remarkably constant over the last 4 billion years, especially considering changes in solar brightness over this time period.

This is climate weathering feedback: Volcanoes put CO2 into the atmosphere and chemical weathering removes it. If something causes climate to warm, weathering will accelerate, but the rate of volcanic eruptions will remain the same. This means that the amount of CO2 in the atmosphere would fall and the climate would cool. If something causes climate to cool, then weathering will slow and CO2 will increase again and the climate will warm back up. This is pertinent to the faint young sun paradox -- over the last 4 billion years the Sun has gradually been getting brighter, but also over that time CO2 has gradually been sequestered in different types of rocks and other geological materials, meaning that the greenhouse strengths has been falling as the Sun has been getting brighter. This can more or less maintain a constant climate.

Describe some of the changes that have occurred in Earth's climate over the last 100 years.

We are able to measure the global average surface temperature and warming is occurring. +0.89°C 1901-2012 +0.72°C 1951-2012 Warming Hiatus: The recent prolonged solar minimum. Increased aerosol pollution since 2000-both industrial and volcanic. Increased heat absorption within the ocean. Changes in Water Cycle: There is more water vapor in the atmosphere. More evaporation of water from Earth's surface at warmer temperatures. There is medium confidence that there has been little overall change in land-based precipitation since 1901. There likely has been an increase in Northern Hemisphere mid-latitude precipitation. For other areas there is low confidence in precipitation trends. Changes in Cryosphere: Less snow cover in the Northern Hemisphere Less sea ice at the end of Arctic summer; slight increase in sea ice at the end of the Antarctic summer. Total mass loss from all glaciers: ~0.62 mm of sea level rise per year (1971-2009), ~0.76 mm of sea level rise per year (1993-2009), ~0.83 mm of sea level rise per year (2008-2009). Greenland is thicker in the middle, thinner at the edges: ~0.09 mm of sea level rise per year (1992-2001) ~0.59 mm of sea level rise per year (2002-20011) Antarctica is thicker in the middle, thinner at some edges: ~0.08mm of sea level rise per year (1992-2001) ~0.40mm of sea level rise per year (2002-2011) Changes in Oceans: Oceans have absorbed 93% of the additional thermal energy in the Earth's climate system It is virtually certain that the upper 700 m of ocean has warmed since 1971 and likely that it warmed from 1870s to 1971. Ocean water has become more acidic as CO2 dissolves in the water. very likely that sea surface salinity has increased. There is medium confidence that the decreased O2 content in ocean can be attributed to human influences. Global Mean Sea Level has risen by 19 cm since 1901. The rate of sea level has accelerated recently. 1.7 mm/yr for 1901 to 2010. 3.2 mm/yr for 1993 to 2010.

***Describe energy use in the United States in terms of energy supply and efficiency.

We get most of our energy from fossil fuels (coal oil and natural gas). Lately we have been using more natural gas and less coal and petroleum. Nuclear has remained about the same. We have seen large percentage increases in the amount of wind and solar energy produced in this country, but as a fraction of the total they have increased from super tiny to tiny. Energy efficiency remains low at about 40%.

***Which of the following glaciers is most likely to completely disappear by the year 2100?

a small mountain glacier in the Rocky Mountains

How much additional warming is predicted to occur in the year 2100 with the RCP 2.6 emission scenario?

about another 1°C

***Which individual is likely to suffer the most from climate change?

an elderly person living in Somalia

The amount of warming that is predicted to occur by the year 2100 by climate models is usually a little less than what is predicted by climate sensitivity alone. Why is this the case?

climate sensitivity does not include the cooling effects of industrial aerosols, which are included in models.

Carbon intensity:

current annual emissions divided by size of economy

***What is a reason why migration may not be an effective way of avoiding the negative consequences of climate change?

developed countries may not allow large numbers of people from foreign countries to enter their countries legally.

***What is a true statement about first-generation biofuels (corn-based ethanol)?

diverting food crops into a transportation fuel has helped drive up the price of food in many parts of the world

***Why is it difficult to be sure that a decline in ecosystem quality was caused by climate change?

ecosystems are under multiple stresses, most of which are unrelated to climate change (e.g. pollution)

What is a true statement about energy efficiency measures?

energy efficiency usually involves purchasing something now that will reduce energy consumption, and therefore costs, in the future

Which of the following is a true statement about Thermohaline Circulation when it is "on"?

glaciers in the region are likely melting.

What will cause a stronger African Monsoon system?

higher eccentricity and perihelion in July

Several different ways of measuring emissions:

historical emissions current emissions emissions per person carbon intensity

***What is a viable mechanism of increasing Earth's reflectivity?

intentionally injecting aerosols into the atmosphere.

What is the best definition of adaptive capacity?

it is a measurement of an individual's ability to purchase something or change their lifestyle as to avoid the negative consequences of climate change

What best compares the total amount of natural and human-caused climate change since 1750?

natural processes have had a small warming effect and human activity has had a large warming effect

Which of the following greenhouse gases has had its concentration fall over the last 250 years?

none; all of their concentrations have increased

What is a correct statement about the uplift weathering hypothesis?

the collision of two continents might lead to cooler temperatures

What is an ethical argument related to reducing the amount of climate change?

the countries with high current and historical emissions have the greatest obligation to reduce their emissions because they have caused the greatest amount of climate change.

***What is contributing the most to sea level rise at the present moment?

the expansion of water that is already in the oceans as it warms up

***Assuming that second generation biofuels can be scaled up and brought to market, what will be the biggest improvement over first-generation biofuels?

the fuel will be created from waste material rather than high-value foods

What best describes the temperature changes over the last 30 years?

the global average temperature has increased

***What is a true statement about people living on low-lying islands?

there is a real risk that rising sea level could completely flood the islands

***What reason was given by U.S. politicians for not entering into binding emission reduction agreements with other countries?

they were worried that if the U.S. agreed to reduce their emissions, but other countries did not agree to the same emission controls, then factories and jobs would move overseas even faster than they were already