Greenhouse Gases, Feedbacks, and Scenarios

What is the relationship between increasing amounts of greenhouse gases and global climate change?  As the NASA article stated, most climate scientists agree the main cause of the current global warming trend is human expansion of the greenhouse effect, warming that result when the atmosphere traps heat radiating from Earth toward space.  Long-lived gases such as aerosols remaining semi-permanently in the atmosphere which do not respond physically or chemically to changes in temperature are described as "forcing" climate change, whereas gases such as water which respond physically or chemically to changes in temperature are seen as "feedbacks."  Gases that contribute to the greenhouse effect include:  Water vapor, Carbon dioxide, Methane, Nitrous oxide, and synthetic compounds of Chlorofluorocarbons.

On Earth, human activities are changing the natural greenhouse.  Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO₂).  This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO₂.  To a lesser extent, the clearing of land for agriculture, industry, and other human activities have increased concentrations of greenhouse gases.

Certain effects seem likely:

• On average, Earth will become warmer.  Some regions may welcome warmer temperatures, but others may not.
• Warmer conditions will probably lead to more evaporation and precipitation overall, but individual regions will vary, some becoming wetter and others dryer.
• A stronger greenhouse effect will warm the oceans and partially melt glaciers and other ice, increasing sea level.  Ocean water also will expand if it warms, contributing further to sea level rise.
• Meanwhile, some crops and other plants may respond favorably to increased atmospheric CO₂, growing more vigorously and using water more efficiently.  At the same time, higher temperatures and shifting climate patterns may change the areas where crops grow best and affect the makeup of natural plant communities.

Aerosols are forcings that can influence climate by scattering light and changing Earth’s reflectivity, they can also alter the climate via clouds.  On a global scale, these aerosol “indirect effects” typically work in opposition to greenhouse gases and cause cooling.  While greenhouse gases disperse widely and have a fairly consistent impact from region to region, aerosol effects are less consistent, partly because of how the particles affect clouds.  In fact, most clouds owe their existence to aerosols that serve as the tiny “seeds,” called cloud condensation nuclei.

Natural aerosols—often sulfates, sea salt, or ammonium salts—are the most common condensation nuclei in pristine environments.  Polluted air, in contrast, usually contains much higher concentrations of water-soluble particles, which means pollution-rich clouds tend to have more numerous, but smaller droplets.  The small droplets make polluted clouds look brighter than they would otherwise.  Just as many bits of crushed ice give light more surfaces to reflect off of, appearing brighter than a solid cube of ice, if the water in a cloud is divided into a larger number of smaller droplets, it will scatter more light and become more reflective.  Despite their small size, they have major impacts on our climate and our health.  http://earthobservatory.nasa.gov/Features/Aerosols/page1.php

In its recently released Fourth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 90 percent probability that human activities over the past 250 years have warmed our planet.  The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 379 parts per million in the last 150 years.  The panel also concluded there's a better than 90 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years.  (Global Climate Change-National Aeronautics and Space Administration) http://climate.nasa.gov/causes/

So, the Woods Hole Research Center said that greenhouse gases act like an insulator or blanket above the earth, keeping the heat in.  Increasing the concentration of these gases in the atmosphere increases the thickness of this insulator, therefore increasing the atmosphere's ability to block the escape of infrared radiation.  Too great a concentration of greenhouse gases can have dramatic effects on climate and significant repercussions for Earth.  Too low a concentration can have dramatic effects as well.  http://www.whrc.org/resources/primer_greenhouse.html

Imperfect understanding of climate feedbacks is a major cause of uncertainty and concern about global warming.  How can the use of climate models help in the understanding of these uncertainties?  Uncertainty is due to the lack of complete knowledge of how the climate works, which will lessen with further study.  Other uncertainty is due to natural variability in the climate system, which will not go away.  And an additional element of uncertainty is due to the inability to predict human behavior and its cumulative impact on the earth’s climate.  The Center on Research for Environmental Decisions stated that Global climate models are used to predict what will happen to Earth’s climate in the future and to help in the understanding of these uncertainties.  Groups like the Intergovernmental Panel on Climate Change (the IPCC) compare the results from several different climate models as they figure out what is most likely to happen.  http://www.cred.columbia.edu/guide/guide/sec5.html

To figure out whether a climate model is doing a good job, scientists give it a test.  The model is run through a time period for which actual measurements of Earth’s climate are gathered, for example the past 100 years.  The results from the model are compared with the actual measurements of real climate.  If the model and the actual measurements are similar, then the math equations in the model that are used to describe how Earth works are probably quite accurate.  If the model results are very different from our records of what actually happened, then the model needs some work. 

Some of the uncertainty about our future climate is because there are processes and feedbacks between different parts of the Earth that are not fully understood.  These are difficult to include in the models until they are better understood.  Today, scientists are conducting research to learn more about how some of the less well-known processes and feedbacks work.  For example, as the Windows to the Universe website stated, the effects of clouds on climate is known to be a large, however it is not fully understood and so scientists are researching clouds to ensure that climate models are as accurate as possible.  Scientists work to ensure that natural processes are represented in climate models as accurately as possible in order for them to be used to make predictions of future climate that are as accurate as possible.

Most of the uncertainty in these predictions of future climate is not related to natural processes.  Instead, it is uncertain how much pollution humans will be adding to the atmosphere in the future.  Innovations that stop or limit the amount of greenhouses gases that are produced, laws and rules that change the amount of pollutants that are released, and how the growing human population lives in the future are all somewhat unknown.  To deal with this, climate models are often run several times, each time with different amounts of pollution and development

http://www.windows2universe.org/earth/climate/cli_models4.html

With regards to the six emission scenarios, what is the evidence existing today that would suggest that one or more of the scenarios may occur within the next 100 years?  There may be evidence existing today that may suggest that the A1T scenario may occur within the next 100 years.  There are different projects toward restoring and conserving the earth by going green and using natural energy sources, such as solar power.  Also, there is a continuous growth in technology now.  I believe that will continue.  Gas prices continue to increase.  As gas prices increase in the US and abroad there will be a shift toward renewable energy sources.  This is already becoming an issue as we see more and more consumers opting for energy efficient cars and hybrids.  Another more recent technology has been the conversion of hydrocarbons or coal to basic fuel that can then be refined into gasoline, kerosene, and other fuels needed.  Some politicians have spoke about nuclear energy as an alternative to coal and there are subsidies currently in place for growing wind and solar technologies.  Wind projects and solar projects have been on the rise.  However, this scenario is highly unlikely because big businesses are too greedy for us to actually go completely with non-fossil fuel energy sources within the next 100 years.  Their mindset is not there as of yet.  http://www.darvill.clara.net/altenerg/

Nevertheless, of the six scenarios A1F1, A1B, A1T, A2, B1, B2 developed by the Intergovernmental Panel on Climate Change (IPCC), the most probable ones that will occur in the next one hundred years is A1B and B1.  A1B scenario’s emphasis is a balance on all resources.  Its driving forces are a rapid economic growth, a rapid growth and then decline in population, and a rapid spread of new and efficient technologies.   B1 scenario’s emphasis is on global solutions to economic, social, and environmental stability.  Its driving forces are a rapid economic growth as in A1B, but with rapid changes towards a service and information economy, a continuous increase of the population, and a reduction in material intensity and the introduction of clean and resource-efficient technologies.  The world will still rely on fossil fuels although other non-fossil fuels will be developed at the same time to “balance” the need as in the A1B scenario.  In motion and happening right now is the development of other non-fossil fuels while at the same time relying on fossil fuels to try to bring balance.  As in the B1 scenario, it is rather easy to introduce clean and resource-efficient technologies on a global scale.  Also, we can well see that we are already in the information age.

What key uncertainties (climate forcings and feedbacks) would exist for these scenarios as a whole or for specific ones individually?  Most probably, key uncertainties would exist for the A1F1, A1T, A2, and B2 scenarios to occur in the next 100 years.  The world will not just depend on fossil fuels within the next 100 years as evident from scientist present designing of hybrid fuels for automobiles.  On the flip side of that, it is highly unlikely that we will actually go completely with non-fossil fuel energy sources within the next 100 years.  Furthermore, we are living in a global village; thus, local or regional solutions will not work. 

Simply stated, A1F1 is most unlikely to happen within the next 100 years because its emphasis is on fossil fuels, but new cleaner non-fossil fuels are being developed.  Also, it is most improbable of A1T happening because a non-fossil energy source solution is ideal, but not realistic.  Non-fossil fuels will take more than the projected time to gradually take place of fossil fuels.  Most likely, it will take over 100 years to have non-fossil fuels totally replace fossil ones.  A2 most likely will not occur because its emphasis is on a world of independently operating and self-reliant nations.  We live in a global village, and the current warming and climate change issue is global.  Thus, working independently doesn’t work.  In a 100 year time span, B2 will also probably fail to occur because its emphasis is on local rather than global solutions to economic, social, and environmental stability.  Again, we live in a global village and the present warming and climate change is a global problem.  Therefore, solutions on the local level aren’t going to be successful either.  Also, as a world community, we are slow to accept more sustainable types of approaches to energies.  For example, an international agreement known as the Kyoto Protocol has been negotiated to reduce greenhouse gas emissions, but the US is not participating in it.  However, as mentioned earlier, A1B and B1 will probably work because A1B emphasizes balance on all resources, which is what we see now, and B1 because it is possible to introduce clean and resource-efficient technologies globally, which this scenario encompasses.  http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf

As a whole, uncertainties exist for these emission scenarios because projecting future emissions differs from other types of prediction that scientists make.  Many natural systems, such as planetary motions, are governed by well-understood physical natural laws.  A third category includes systems to which the concept of governing laws expressed by mathematical equations is not applicable (Gaffin, 2002).  For these systems, the driving forces change over time, sometimes radically, making prediction of specific outcomes a speculative effort.  Many social, political, and economic science systems would fall into this category.  Future anthropogenic emissions are a function of such socioeconomic systems and, as a result, are inherently unpredictable.  The National Academies Press states that although projections of future population are thus readily available for use in emissions models, long-term projections for the other key socioeconomic factors that drive emissions are generally not available, and they are unpredictable.  All the driving forces not only influence CO2 emissions, but also the emissions of other GHGs.  Therefore, uncertainties for these scenarios exist.  http://www.nap.edu/openbook.php?record_id=11175&page=109