Global Warming (Part (II)

Effects

Projections of global mean sea level rise by Parris and others.  Probabilities have not been assigned to these projections. Therefore, none of these projections should be interpreted as a "best estimate" of future sea level rise.

Sparse records indicate that glaciers have been retreating since the early 1800s. In the 1950s measurements began that allow the monitoring of glacial mass balance, reported to the World Glacier Monitoring Service (WGMS) and the National Snow and Ice Data Center (NSIDC).

Biosphere

Overall, it is expected that climate change will result in the extinction of many species and reduced diversity of ecosystems.  Rising temperatures have been found to push bees to their physiological limits, and could cause the extinction of bee populations. A 2012 study concluded that continued ocean uptake of CO2 affects the brains and central nervous system of certain fish species and this impacts their ability to hear, smell, and evade predators. The study authors note, "We've now established it isn't simply the acidification of the oceans that is causing disruption – as is the case with shellfish and plankton with chalky skeletons – but the actual dissolved CO2 itself is damaging the fishes' nervous systems."

Environmental

 As the climate change melts sea ice, the U.S. Geological Survey projects that two-thirds of polar bears will disappear by 2050.

The environmental effects of global warming are broad and far reaching. They include the following diverse effects:

Arctic sea ice decline, sea level rise, retreat of glaciers: Global warming has led to decades of shrinking and thinning in a warm climate that has put the Arctic sea ice in a precarious position, it is now vulnerable to atmospheric anomalies.  Projections of declines in Arctic sea ice vary.  Recent projections suggest that Arctic summers could be ice-free (defined as ice extent less than 1 million square km) as early as 2025–2030.  The sea level rise since 1993 has been estimated to have been on average 2.6 mm and 2.9 mm per year ± 0.4 mm. Additionally, sea level rise has accelerated from 1995 to 2015.  Over the 21st century, the IPCC projects for a high emissions scenario, that global mean sea level could rise by 52–98 cm.

Extreme weather, extreme events, tropical cyclones: Data analysis of extreme events from 1960 until 2010 suggests that droughts and heat waves appear simultaneously with increased frequency.  Extremely wet or dry events within the monsoon period have increased since 1980.  Projections suggest a probable increase in the frequency and severity of some extreme weather events, such as heat waves.

Ecosystem changes, changes in ocean properties: In terrestrial ecosystems, the earlier timing of spring events, as well as poleward and upward shifts in plant and animal ranges, have been linked with high confidence to recent warming.  It is expected that most ecosystems will be affected by higher atmospheric CO2 levels, combined with higher global temperatures. Expansion of deserts in the subtropics is probably linked to global warming. The physical effect of global warming on oceans includes an increase in acidity, and a reduction of oxygen levels (ocean deoxygenation). Increases in atmospheric CO2 concentrations have led to an increase in dissolved CO2 and thus ocean acidity, measured by lower pH values. Ocean acidification threatens damage to coral reefs, fisheries, protected species, and other natural resources of value to society. Without substantial actions to reduce the rate of global warming, land based ecosystems are at risk of major ecological shifts, transforming composition and structure.

Long-term effects of global warming, runaway climate change: On the timescale of centuries to millennia, the magnitude of global warming will be determined primarily by anthropogenic CO2 emissions. This is due to carbon dioxide's very long lifetime in the atmosphere. Long-term effects also include a response from the Earth's crust, due to ice melting and deglaciation, in a process called post-glacial rebound, when land masses are no longer depressed by the weight of ice. This could lead to landslides and increased seismic and volcanic activities. Tsunamis could be generated by submarine landslides caused by warmer ocean water thawing ocean-floor permafrost or releasing gas hydrates.

Abrupt climate change, cold blob (North Atlantic): Climate change could result in global, large-scale changes in natural and social systems.  Examples include ocean acidification caused by increased atmospheric concentrations of carbon dioxide, and the long-term melting of ice sheets, which contributes to sea level rise.  Some large-scale changes could occur abruptly, i.e., over a short time period, and might also be irreversible. Examples of abrupt climate change are the rapid release of methane and carbon dioxide from permafrost, which would lead to amplified global warming. Another example is the possibility for the Atlantic Meridional Overturning Circulation to slow- or shutdown.  This could trigger cooling in the North Atlantic, Europe, and North America.  It would particularly affect areas such as the British Isles, France and the Nordic countries, which are warmed by the North Atlantic drift.

Social systems

The effects of climate change on human systems, mostly due to warming or shifts in precipitation patterns, or both, have been detected worldwide. The future social impacts of climate change will be uneven across the world. Many risks are expected to increase with higher magnitudes of global warming.  All regions are at risk of experiencing negative impacts.  Low-latitude, less developed areas face the greatest risk.  A study from 2015 concluded that economic growth (gross domestic product) of poorer countries is much more impaired with projected future climate warming, than previously thought.  In small islands and mega deltas, inundation as a result of sea level rise is expected to threaten vital infrastructure and human settlements.  This could lead to issues of homelessness in countries with low-lying areas such as Bangladesh, as well as statelessness for populations in countries such as the Maldives and Tuvalu.

Examples of impacts of global warming on humans include:

·         A meta-analysis concluded in 2014 that each degree of temperature rise will increase violence by up to 20%, which includes fist fights, violent crimes, civil unrest, or wars.

·         Estimates in 2015 based on the IPCC A1B emission scenario from additional greenhouse gases released from permafrost, found associated impact damages to the economy to be US$43 trillion.

Crop production will probably be negatively affected in low latitude countries, while effects at northern latitudes may be positive or negative.  Global warming of around 4.6 °C relative to pre-industrial levels could pose a large risk to global and regional food security.  The impact of climate change on crop productivity for the four major crops was negative for wheat and maize and neutral for soy and rice in the years 1960-2013.  While crop production has increased in some mid-latitude regions such as the UK and Northeast China, economic losses due to extreme weather events have increased globally.

Generally impacts on public health will be more negative than positive.  Impacts include: the effects of extreme weather, leading to injury and loss of life; and indirect effects, such as under-nutrition brought on by crop failures. There has been a shift from cold- to heat-related mortality in some regions as a result of warming. A 2018 study of data from the U.S. Centers for Disease Control and Prevention connected temperature rise to increased numbers of suicides. The study revealed that hotter days could increase suicide rates and could cause approximately 26,000 more suicides in the U.S. by 2050.

Livelihoods of indigenous peoples of the Arctic have been altered by climate change, and there is emerging evidence of climate change impacts on livelihoods of indigenous peoples in other regions. Regional impacts of climate change are now observable at more locations than before, on all continents and across ocean regions.

Regional

The Arctic, Africa, small islands and Asian mega-deltas are regions that are likely to be especially affected by future climate change.  Africa is one of the most vulnerable continents to climate variability and change because of multiple existing stresses and low adaptive capacity.  Existing stresses include poverty, political conflicts, and ecosystem degradation. By 2050, between 350 million and 600 million people are projected to experience increased water stress due to climate change.  Climate variability and change is projected to severely compromise agricultural production, including access to food, across Africa.  Research projects that regions even may become uninhabitable, due to a high wet-bulb temperature.

Responses

Mitigation

The graph on the right shows three "pathways" to meet the UNFCCC's 2 °C target, labelled "global technology", "decentralized solutions", and "consumption change". Each pathway shows how various measures (e.g., improved energy efficiency, increased use of renewable energy) could contribute to emissions reductions.

Mitigation of climate change are actions to reduce greenhouse gas emissions, or enhance the capacity of carbon sinks to absorb greenhouse gases from the atmosphere.  There is a large potential for future reductions in emissions by a combination of activities, including energy conservation and increased energy efficiency; the use of low-carbon energy technologies, such as renewable energy, nuclear energy, and carbon capture and storage; and enhancing carbon sinks through, for example, reforestation and preventing deforestation.  A 2015 report by Citibank concluded that transitioning to a low carbon economy would yield positive return on investments.

Near- and long-term trends in the global energy system are inconsistent with limiting global warming at below 1.5 or 2 °C, relative to pre-industrial levels.  Pledges made as part of the Cancún agreements are broadly consistent with having a likely chance (66 to 100% probability) of limiting global warming (in the 21st century) at below 3 °C, relative to pre-industrial levels.

In limiting warming at below 2 °C, more stringent emission reductions in the near-term would allow for less rapid reductions after 2030.  Many integrated models are unable to meet the 2 °C target if pessimistic assumptions are made about the availability of mitigation technologies.

Adaptation

Climate change adaptation is another policy response. The adaptation may be planned, either in reaction to or anticipation of global warming, or spontaneous, i.e., without government intervention.  Planned adaptation is already occurring on a limited basis.  The barriers, limits, and costs of future adaptation are not fully understood.  Environmental organizations and public figures have emphasized changes in the climate and the risks they entail, while promoting adaptation to changes in infrastructural needs and emissions reductions.

Adaptation is especially important in developing countries since those countries are predicted to bear the brunt of the effects of global warming. That is, the capacity and potential for humans to adapt (called adaptive capacity) is unevenly distributed across different regions and populations, and developing countries generally have less capacity to adapt.

Climate engineering

Climate engineering (sometimes called geoengineering or climate intervention) is the deliberate modification of the climate. It has been investigated as a possible response to global warming, e.g. by NASA and the Royal Society. Techniques under research fall generally into the categories solar radiation management and carbon dioxide removal, although various other schemes have been suggested. A study from 2014 investigated the most common climate engineering methods and concluded they are either ineffective or have potentially severe side effects and cannot be stopped without causing rapid climate change.

Society and culture

Political discussion

Article 2 of the UN Framework Convention refers explicitly to "stabilization of greenhouse gas concentrations".  To stabilize the atmospheric concentration of CO2, emissions worldwide would need to be dramatically reduced from their present level.

Most countries in the world are parties to the United Nations Framework Convention on Climate Change (UNFCCC).  The ultimate objective of the Convention is to prevent dangerous human interference of the climate system.  As stated in the Convention, this requires that greenhouse gas concentrations are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can proceed in a sustainable fashion.  The Framework Convention was agreed on in 1992, but global emissions have risen since then.

During negotiations, the G77 (a lobbying group in the United Nations representing 133 developing countries) pushed for a mandate requiring developed countries to "[take] the lead" in reducing their emissions.  This was justified on the basis that the developed countries' emissions had contributed most to the cumulation of greenhouse gases in the atmosphere, per-capita emissions (i.e., emissions per head of population) were still relatively low in developing countries, and the emissions of developing countries would grow to meet their development needs.

This mandate was sustained in the Kyoto Protocol to the Framework Convention, which entered into legal effect in 2005.  In ratifying the Kyoto Protocol, most developed countries accepted legally binding commitments to limit their emissions. These first-round commitments expired in 2012.  United States President George W. Bush rejected the treaty on the basis that "it exempts 80% of the world, including major population centres such as China and India, from compliance, and would cause serious harm to the US economy".

At the 15th UNFCCC Conference of the Parties, held in 2009 at Copenhagen, several UNFCCC Parties produced the Copenhagen Accord.  Parties associated with the Accord (140 countries, as of November 2010):  9 aim to limit the future increase in global mean temperature to below 2 °C. The 16th Conference of the Parties (COP16) was held at Cancún in 2010. It produced an agreement, not a binding treaty, that the Parties should take urgent action to reduce greenhouse gas emissions to meet a goal of limiting global warming to 2 °C above pre-industrial temperatures. It also recognized the need to consider strengthening the goal to a global average rise of 1.5 °C.

Scientific discussion

The discussion continues in scientific articles that are peer-reviewed and assessed by scientists who work in the relevant fields and participate in the Intergovernmental Panel on Climate Change. The scientific consensus as of 2013 stated in the IPCC Fifth Assessment Report is that it "is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century".  A 2008 report by the U.S. National Academy of Sciences stated that most scientists by then agreed that observed warming in recent decades was primarily caused by human activities increasing the amount of greenhouse gases in the atmosphere.  In 2005 the Royal Society stated that while the overwhelming majority of scientists were in agreement on the main points, some individuals and organizations opposed to the consensus on urgent action needed to reduce greenhouse gas emissions had tried to undermine the science and work of the IPCC. National science academies have called on world leaders for policies to cut global emissions.

In 2018, the IPCC published SR15, which warned that if current rate of greenhouse gas emissions are not mitigated, major crises could occur by 2040 as the planet warms by 2.7 degrees Fahrenheit (1.5 degrees Celsius). The report said that preventing such crises will require a swift transformation of the global economy that has "no documented historic precedent."

In the scientific literature, there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused mainly by human-induced emissions of greenhouse gases.  No scientific body of national or international standing disagrees with this view.  In November 2017, a second warning to humanity signed by 15,364 scientists from 184 countries stated that "the current trajectory of potentially catastrophic climate change due to rising greenhouse gases from burning fossil fuels, deforestation, and agricultural production – particularly from farming ruminants for meat consumption" is "especially troubling".  A July 2017 study published in Environmental Research Letters asserts that the most significant action individuals could make to mitigate their own carbon footprint is to have fewer children, followed by living vehicle free, forgoing air travel and adopting a plant-based diet.

Public opinion and disputes

The global warming controversy refers to a variety of disputes, substantially more pronounced in the popular media than in the scientific literature, regarding the nature, causes, and consequences of global warming. The disputed issues include the causes of increased global average air temperature, especially since the mid-20th century, whether this warming trend is unprecedented or within normal climatic variations, whether humankind has contributed significantly to it, and whether the increase is completely or partially an artefact of poor measurements. Additional disputes concern estimates of climate sensitivity, predictions of additional warming, and what the consequences of global warming will be.

In the United States from about 1990 onwards, American conservative think tanks had begun challenging the legitimacy of global warming as a social problem. They challenged the scientific evidence, argued that global warming would have benefits, and asserted that proposed solutions would do more harm than good. Some people dispute aspects of climate change science.  Organizations such as the libertarian Competitive Enterprise Institute, conservative commentators, and some companies such as ExxonMobil have challenged IPCC climate change scenarios, funded scientists who disagree with the scientific consensus, and provided their own projections of the economic cost of stricter controls.  On the other hand, some fossil fuel companies have scaled back their efforts in recent years, or even called for policies to reduce global warming. Global oil companies have begun to acknowledge climate change exists and is caused by human activities and the burning of fossil fuels.

The global warming problem came to international public attention in the late 1980s. Polling groups began to track opinions on the subject, at first mainly in the United States. The longest consistent polling, by Gallup in the US, found relatively small deviations of 10% or so from 1998 to 2015 in opinion on the seriousness of global warming, but with increasing polarization between those concerned and those unconcerned.

Due to confusing media coverage in the early 1990s, issues such as ozone depletion and climate change were often mixed up, affecting public understanding of these issues.  According to a 2010 survey of Americans, a majority thought that the ozone layer and spray cans contribute to global warming. Although there are a few areas of linkage, the relationship between the two is not strong. Reduced stratospheric ozone has had a slight cooling influence on surface temperatures, while increased tropospheric ozone has had a somewhat larger warming effect.  However, the CFC's used in spray cans are powerful greenhouse gases, with some estimates attributing CFC emissions during the 70s to have caused almost half of the global warming for that decade.

By 2010, with 111 countries surveyed, Gallup determined that there had been a substantial decrease since 2007–2008 in the number of Americans and Europeans who viewed global warming as a serious threat. In the US, just a little over half the population (53%) viewed it as a serious concern for either themselves or their families; this was 10 points below the 2008 poll (63%). Latin America had the biggest rise in concern: 73% said global warming was a serious threat to their families.  This global poll also found that people were more likely to attribute global warming to human activities than to natural causes, except in the US where nearly half (47%) of the population attributed global warming to natural causes.

A March–May 2013 survey by Pew Research Center for the People & the Press polled 39 countries about global threats. According to 54% of those questioned, global warming featured top of the perceived global threats.

History

The history of climate change science began in the early 19th century when ice ages and other natural changes in paleo-climate were first suspected and the natural greenhouse effect first identified.  In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate. In the 1960s, the warming effect of carbon dioxide gas became increasingly convincing.  By the 1990s, as a result of improving fidelity of computer models and observational work confirming the Milankovitch theory of the ice ages, a consensus position formed: greenhouse gases were deeply involved in most climate changes and human caused emissions were bringing discernible global warming. Since the 1990s, scientific research on climate change has included multiple disciplines and has expanded.  Research during this period has been summarized in the Assessment Reports by the Intergovernmental Panel on Climate Change.

Terminology

In the 1950s, research suggested increasing temperatures, and a 1952 newspaper reported "climate change". This phrase next appeared in a November 1957 report in The Hammond Times which described Roger Revelle's research into the effects of increasing human-caused CO2 emissions on the greenhouse effect, "a large scale global warming, with radical climate changes may result". Both phrases were used only occasionally until 1975, when Wallace Smith Broecker published a scientific paper on the topic, "Climatic Change: Are We on the Brink of a Pronounced Global Warming?" The phrase began to come into common use, and in 1976 Mikhail Budyko's statement that "a global warming up has started" was widely reported. Other studies, such as a 1971 MIT report, referred to the human impact as "inadvertent climate modification", but an influential 1979 National Academy of Sciences study headed by Jule Charney followed Broecker in using global warming for rising surface temperatures, while describing the wider effects of increased CO2 as climate change.

In 1986 and November 1987, NASA climate scientist James Hansen gave testimony to Congress on global warming. There were increasing heatwaves and drought problems in the summer of 1988, and when Hansen testified in the Senate on 23 June he sparked worldwide interest.  He said, "global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and the observed warming."  Public attention increased over the summer, and global warming became the dominant popular term, commonly used both by the press and in public discourse.

In a 2008 NASA article on usage, Erik M. Conway defined global warming as "the increase in Earth's average surface temperature due to rising levels of greenhouse gases", while climate change was "a long-term change in the Earth's climate, or of a region on Earth". Because effects such as changing patterns of rainfall and rising sea levels would probably have more impact than temperatures alone, he considered global climate change a more scientifically accurate term, and like the Intergovernmental Panel on Climate Change, the NASA website emphasized this wider context.