ENVR Issues: Ch. 19 - Climate Change
What is Consensus? Is there a consensus on global warming?
- Because climate scientists don't know precisely what the future holds in terms of the amount of warming that will occur and the resulting impacts of global warming, a door remains open for skeptics to argue that "there isn't a scientific consensus on global warming." But there is A LOT of consensus, and the number of studies rejecting anthropocentric global warming is decreasing, becoming an insanely small proportion of published research. - 97% of climate scientists agree that humans are causing global warming. - People misunderstand the word "consensus." Consensus does not mean total unanimity, and total unanimity is rare anywhere in science, and unanimity is not a prerequisite for scientific acceptance. *Consensus Definition*: a general agreement; the judgement arrived at by most of those concerned; group solidarity in sentiment and belief. Scientific consensus exists on most of global warming's most important issues, including a vast majority of scientists agreeing on the following: 1. The physics of the greenhouse effect. The greenhouse effect is a naturally occurring phenomenon, whereby greenhouse gases regulate the earth's surface temperature. 2. Since the beginning of the industrial revolution, humans have dramatically increased levels of greenhouse gases in the troposphere by use of fossil fuels, farming, use of inorganic fertilizers, burning forests, etc. Greenhouse gases are at their highest levels in 160,000 years. 3. Over the 140 years of weather observations, global surface temperatures have been rising. 4. Most importantly, the earth is warming, mostly because of human actions. Global warming is occurring. Scientists HAVE come to consensus that rising surface temperatures are a result of human-induced changes in atmospheric greenhouse gases. The amount of warming expected to occur and what impacts these will have remain significant and very consequential questions, BUT the notion that global warming is unproven is a minority opinion mostly supported by non-experts (w/ political agendas), industry lobbying groups (w/ economic agendas), and a small number of climate scientists (less than 3%).
Possible "Benefits" of a Warmer World, and their flaws
- Cost of heating might decline, as well as energy consumption. - Northern latitudes might become more suitable for human settlement. Expanded habitats and ranges of animal life. - Could increase rainfall in some areas, and thus food production. - CO2 is a plant fertilizer, so 1% increases in CO2 increase the rate of photosynthesis. Almost every "potential beneficial effect" of global warming in one place or during one season would be offset by huge negative effects in another place or a different season. Disruptions to the environment, economy, lifestyle, etcetera would not be evenly distributed, but they would be widespread and globally disruptive!
Anthropogenic Climate Change: Atmospheric Warming
- Earth's climate fluctuates over billions of years, ice ages and interglacial periods. Climate changes are somewhat natural in slow phases. The tilting of the Earth's axis impacts air flows to change climate. Huge volcanic events covered the atmosphere, or big meteor strikes put debris in the atmosphere. Seismic events/tectonics. Sunspot flares (changes in sun's radiation). Etcetera. - We are in a warmer interglacial period so its generally natural. But as you close in on the scale, the warming is much more significant than the normal pace. - 20th century was the hottest century in the past 1000 years. 1906-2015 mean global temperatures have risen 1 degree Celsius (1.8 F), and most of this increase occurred since the mid 1970's. *Mean global temperatures are increasing and occurring with an absence of normal environmental factors that would cause such changes*. - 2014 IPCC report stated it is very likely (90% certain) that the Earth's mean surface temperature would increase by 1.5-4.0 C (2.7-8.1 F) between 2013 and 2100, unless deforestation and greenhouse gas emissions are sharply reduced. - - The high end will have huge problems, low end might be livable. The range is a problem, and there is much uncertainty on predicting future warming as well as the impacts of the warming.
Possible Harmful Effects of a Warmer World: Human Health Impacts
5. Human Health Impacts - More heat waves, disruption of food and water supplies, alteration of disease patterns (eg. malarial mosquitoes moving with shifting climates to less resistant areas), bacteria levels (leading to food spoilage), etcetera. - These impacts can have immense direct effects on human health. So would environmental refugees crossing borders, causing social disorder, political unrest, and even war. - Basically all of the prior 4 effects would have extremely negative impacts on human life. The possible impacts of climate change, to the environment, human health, societies and economies, are far-ranging and devastating. It is difficult to identify a singular environmental problem with more far-reaching impacts, or representing a greater potential threat to the future of life on earth.
Areas of Un/Certainty on Anthropogenic Climate Change: Are We Already Experiencing Climate Change?
Certain consensus opinion on this question: - Greenhouse gas concentrations are increasing, and global temperature is increasing. There is a tight positive correlation between CO2 in the atmosphere and average atmospheric temperature. Correlation≠causation, and the consensus opinion of scientists believes that they are correlated, but there is a small amount of debate over a causal link between the two. - Greenhouse gases are increasing (fact), and *natural factors on Earth that could explain our changing climate/atmospheric warming have not been found*. Because no natural drivers have been found, *anthropogenic factors are the only way to explain global warming*. - The vast majority of scientists believe that greenhouse gases and temperature increases are causally linked because the physics of the greenhouse effect are well understood, because it is an accepted fact that greenhouse gas concentrations are rising in the atmosphere as a result of human activities like fossil-fuel burning, and IMPORTANTLY because natural drivers that might otherwise explain rising global temperatures have not been found in almost 30 years of scientific evidence.
The Greenhouse Effect
- Gases known as greenhouse gases absorb and emit infrared radiation, which is not in or near the visible spectrum. - In order of abundance, the 4 most abundant greenhouse gases are: water vapor (H2O), Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O). - Greenhouse gases regulate Earth's surface temperature through the greenhouse effect. Greenhouse gases act as glass to greenhouses - allow sunlight into the Earth, then traps the heat energy in. - Sun's heat energy comes to Earth (shortwave radiation passes through troposphere); sunlight is absorbed into Earth and degrades into longer wave IR heat energy; some heat is trapped in the earth while some heat bounces back out into space, etc. Heat energy is trapped by the greenhouse gases (a lot is reflected back onto earth). - This is a natural heat trapping process of the atmosphere. Without greenhouse gases, the earth would be 0 degree Fahrenheit average. It is a natural and good thing to happen. - - The problem is that humans are increasing the greenhouse gas concentration and amplifying the natural greenhouse effect (anthropogenic climate change and atmospheric warming). Atmospheric Warming and Anthropogenic Climate Change: Warming of the Earth's lower atmosphere as a result of increases in the concentrations of greenhouse gases from human activity.
Anthropogenic Climate Change: Rising Greenhouse Gas Concentrations
- There is clear evidence that greenhouse gas concentration has increased - sharp increase since industrial revolution in CO2. - Average atmospheric concentration of CO2 rose by ~38% from 1880-2015, with more than half of this increase happening since 1970. - CO2 naturally occurs at 0.036% in the atmosphere, and human activity is increasing it substantially. Human activity impacts CO2 the most, and CO2 has the most significant heat trapping effect because of this elevated concentration. - CO2 concentration measured from atmosphere since 1960 - very clear and consistent increase. Concentrations of CO2 from before 1960 is done with paleo records (ice cores) indirectly. Ice holds tiny bits of atmosphere in glaciers (striated layers from each year with the snow/ice deposited). Layers of ice from 300 years ago still holds trapped air, CO2 levels measured from that. These measurements show that he trajectory is accurate. Other Greenhouse Gases: - Methane (CH4) levels have risen by 160%, and ice core analyses suggest 70% of methane emissions in the last 275 years are the result of human activities. - Nitrous Oxide (N2O) levels have increased by 20% in the last 275 years, mostly because of increased use of nitrogen fertilizers and automobiles. - CH4 has 25x more heat trapping ability than CO2, and N2O is 300x as potent as CO2. - Overall there has been a 70% increase in GG concentrations since 1970. Paleoclimatologists believe GG levels in the troposphere are the highest they have been in the past 160,000 years. - IPCC is the world's leading source of climate change data/info (Intergovernmental Panel on Climate Change). It digests, reviews, and summarizes the world's climate research. Data represents the current state of climate knowledge, and produces the consensus climate opinion.
Possible Harmful Effects of a Warmer World: Food and Water Supplies
1. *Food and Water Supplies* - Global warming is expected to shift climate belts poleward, expanding tropical zones, pushing midlatitude zones poleward, and shrinking polar zones. This will dramatically alter temperature and precipitation patterns, and disrupt global food production and water availability relative to established populations and economies. - It is foolish to think we could adapt and move quickly to adhere to this. On top of climate, you need proper soil, flat terrain, etc. You can't simply shift climate conditions poleward and easily accommodate it. - Global food production and water supplies would be severely disrupted by a significant shift in climate conditions. Very few areas would benefit, and the hardest hit places by climate change would be areas already struggling to feed their populations. Places that become drier are population centers now (because people settled there for optimal resources). - In general, systems would be disrupted in terms of food/water growth and delivery. The developing world would have severe impacts with high human costs.
HW 12: Climate Change Tipping Points
1. Define climate change tipping point. - *Tipping elements* are components of the climate system that could pass *climate change tipping points*: the thresholds beyond which natural systems could change for hundreds to thousands of years, with possibly catastrophic effects. 2. List examples of climate change tipping points as highlighted in figure 19.9. - One tipping element is *atmospheric CO2 levels*. We need to prevent CO2 levels from exceeding 450 ppm, or else passing that tipping point may result in experiencing large-scale climate changes that would last for hundreds to thousands of years. We have already reached 400 ppm, and without strong efforts to improve energy efficiency and replace fossil fuels with low-carbon energy resources, we could exceed 450 ppm within a couple of decades. - Another tipping element is *global average atmospheric pressure*. Several findings on atmospheric warming suggest we can no longer avoid a global temperature rise of more than 2 C (3.6 F), the threshold beyond which will be very dangerous.
Causes of Anthropogenic Greenhouse Gas Increases
1. Fossil Fuel Combustion (oil, coal, natural gas) - Above all else, this leads in CO2, NO2, and CH4 production. 2. Deforestation - Vegetation stores carbon in its tissue, and green plant photosynthesis turns CO2 + water + sun --> stored carbon in tissues. Cutting down trees releases the carbon from the trees as CO2 in the atmosphere - removing a carbon sink. - Once cut down, the vegetation is often burned, which immediately releases all of the carbon into the atmosphere (instead of slowing the carbon release by reusing wood). 3. Commercial Agriculture - Inorganic chemical fertilizers are the leading cause of N2O production. - CH4 production from cows and livestock (poop), and landfills generate CH4. The developed world accounts for the vast majority of current CO2 emissions. China and the US are the world's largest CO2 polluters. CO2 emissions of 7 countries were responsible for 60% of atmospheric warming taking place from 1906 to today. In order, they are: US, China, Russia, Brazil, India, Germany, UK. - Countries with the highest per capita CO2 emissions: Australia, US, Canada.
Possible Harmful Effects of a Warmer World: Rising Sea Levels
2. *Rising Sea Levels* - Global sea level has already risen *7in. (19cm) in the past century*, and its expected to continue rising by 40-60cm (1.3-2.0ft.) by the end of this century. The range of possible sea level rise is wide, but future impacts to infrastructure, biodiversity, agriculture, etc. could be devastating. - 2 main reasons: melting polar ice caps, and importantly *the thermal expansion of water* (accounts for 2/3 of sea level rise - heated water expands). - Estimated 20% of arctic sea ice has been lost since 1979. Temperature increases are more severe in polar regions, so polar ice melting was the first warning sign of climate change in the average temperature of earth's troposphere. - - The polar ice caps help keep temperatures down on earth, reflecting 80-90% of sunlight back into space, but with it melting it reflects less sunlight and allows the troposphere to warm further. - - Loss of ice also means an overall loss of freshwater in the global hydrologic cycle. - Continued sea level rise depends on the heat of the atmosphere, but a worst case scenario shows coastal areas (with 1/3 of the world's population) getting flooded and wrecked. There are huge population centers (as well as economic and industrial infrastructure) located in low-lying coastal areas that are vulnerable to sea level rise. Food production problems would escalate, pollution would increase from the flooding of coastal industrial systems, and there would be massive biodiversity impacts to the affected ecosystems.
Possible Harmful Effects of a Warmer World: Biodiversity Impacts
3. Biodiversity Impacts - Climate conditions affect plant and animal life, and such life is adapted to particular climate conditions. If climate conditions are altered, the capacity of the environments to support its plants and animals will diminish. The location of many of the world's biomes would be changed by shifting climates. Plants and animals would have to adapt to changing climate conditions, migrate with shifting climates, or simply die. - Biodiversity impacts would be staggering. - - Eg: US climate shifts northward, trees will find their areas inhospitable that used to be optimal. Seeds must go north, or the trees will perish. Not all living things can adapt and migrate. Tree species may not migrate fast enough, and its possible that many forest biomes would become extinct. - Specific biodiversity impacts remain unknown, but many climate scientists and ecologists believe that a potential mass extinction event could be triggered by anthropogenic climate change, akin to the loss of the dinosaurs millions of years ago.
Possible Harmful Effects of a Warmer World: Extreme Weather Changes
4. Extreme Weather Changes - Elevated levels of heat at the earth's surface would create higher average wind speeds, more clashing warm and cold fronts, and generally more vigorous and violent weather. Many climatologists predict increased intensity and frequency of damaging floods, hurricanes, tornadoes, blizzards, and violent storms. - In addition to the loss of human life, increased incidences of violent weather would have immense economic impacts by disrupting economic activity, displacing people, and bankrupting insurance and banking industries. It would also amplify impacts to biodiversity through loss of plant/animal life and habitat destruction.
The Atmosphere
About 75% of the earth's air is found in the innermost atmospheric layer, the troposphere, which extends about 9-12 miles above sea level. The troposphere is made up of nitrogen (78%), oxygen (21%), with smaller amounts of water vapor, argon, CO2, and other gases. The atmosphere is the thin envelope of life sustaining gases that support and protect all life on Earth. Changes in the concentration of a set of gases in the troposphere are what we're concerned about in climate warming, particularly greenhouse gases.
Ethical Decision-Making on Global Warming: *The No-Regrets Strategy*
Another ethical decision making strategy is the *no-regrets strategy*: even if anthropogenic climate change does not occur, even if the impacts are shown to have been overestimated, the steps taken to alleviate the threat of climate change now have environmental, health, and economic benefits that society must take regardless of climate change. - For example, regardless of climate change's existence, converting away from fossil fuel use must occur eventually anyways because they are non-renewable fuels, they generate harmful air pollutants, our reliance of them is a national security issue, etc. - For example, regardless of climate change's existence, halting deforestation has important environmental advantages including biodiversity protection, watershed protection, etc.
Areas of Un/Certainty on Anthropogenic Climate Change: How Much Warming Is Likely To Occur, And What Are The Likely Effects?
Much more uncertainty on this question: - A number of natural and human-influenced factors influence global climate, and depending on how these factors interact they may amplify or dampen projected changes in the average temperature of the troposphere. These factors which we are highly uncertain about are known as *climate feedback mechanisms*, and significant uncertainty surrounds many of them. - The role of cloud cover is a perfect example of a climate feedback mechanism. A warmer global climate would result in more evaporation of water at the earth's surface and increased global cloud cover, but would the increased cloud over increase the effects of global warming or dampen temperature increases? - - Additional clouds may have a warming effect by insulating the earth like a blanket and trapping heat energy close to the earth - an *insulating effect* increases global warming. - - Additional cloud cover could have a cooling effect by shading the planet and reflecting more incoming sunlight back into space - a *shading effect* decreases global warming. - - Several factors will affect the net result of more cloud cover, such as the amount of water vapor in the troposphere, whether clouds are thin or thick, coverage, altitude of the cloud, size and number of water droplets or ice crystals formed in clouds, etc. - Uncertainty surrounding the role of cloud cover and many other climate feedback mechanisms are largely responsible for the wide range of predictions climate scientists produce regarding future temperature increases. If their predictions for future are at the lower end of predictions (1.5 C by 2100) global warming may be impactful but not devastating; if they come at the higher end of the spectrum (4.5 C by 2100) the impacts may be devastating.
Solutions to Anthropogenic Climate Change
Reduce Greenhouse Gas Emissions: - *Improve energy efficiency*. Quickest, cheapest, and most effective way to immediately reduce CO2 emissions. - *Develop renewable energy resources*. Increase reliance on cleaner fossil fuels such as natural gas as we eliminate dirty fuels such as coal and oil. Must develop renewable, non-polluting forms of energy as quickly as possible. Tax or Cap Greenhouse Gas Emissions: - There are a wide variety of regulatory approaches to reducing greenhouse gas emissions. Most involve placing a price on carbon and other greenhouse gas emissions so that industry and consumers begin paying the real price (one that reflects the harmful environmental costs) of fossil fuel use. Two approaches: - - The *Carbon and Energy Tax* approach involve government placing a tax on fossil fuels based on their carbon content. Traditional fuels like coal and oil would become more expensive to use, discouraging their use and encouraging the use of untaxed (and now made cheaper) fuels like wind and solar power. Some countries like Japan and Australia have implemented carbon tax systems (the US has not). - The *Cap and Trade Policy* approach would have governments place a total cap on carbon pollution/emissions, slowly lowering the cap over time. All industry must work together to keep their emissions below the carbon cap. A market is created for carbon allowanced (allocated pollution credits) that industry can trade among themselves. Industry can make money by reducing their carbon emissions and selling their carbon allowances to other industries who haven't yet found ways to reduce their carbon emissions. This is a free-market approach to pollution regulation. Individuals Matter! - There is much an individual can do to reduce CO2 and other greenhouse gas emissions. Recognizing that individual decisions, when they occur in mass, have the ability to affect major change.
Ethical Decision-Making on Global Warming: *The Precautionary Approach*
There are other ways to think about and evaluate the debate in favor of acting now on climate change. Ethical decision-making can help us wade through the science and make decisions about whether climate change is worth doing something about. Strong scientific consensus has been reached on most anthropogenic climate change issues and given the potential impacts there are many reasons to be concerned, with possibly enormous impacts that threaten the future viability of life on Earth more than any other phenomena. Therefore, siding with the scientific majority and erring on the side of caution makes far more sense than denying the likely threat of climate change. The scientific evidence suggests that ethically, a precautionary strategy is in order when it comes to dealing with the possible effects of global warming: that it is best to take action now before it is too late to reverse the impacts of climate change.