Among legitimate scientists, there is an overwhelming consensus on the reality of climate change. Virtually all professional climate scientists agree on the reality of human-induced climate change, but debate continues on tempo and mode.
The world is "neither prepared to slow down climate change, nor to live with it." climate change is the emblematic problem of the Anthropocene: it is both a driver and a symbol of a thoroughly transformed world. Anthropogenic climate change is primarily a consequence of burning fossil fuels and deforestation.
In the conditions of the Anthropocene, many natural disasters have become “unnatural”ones. The conditions for the recent fires in Maui, for example, were established through record sea-surface temperatures, rising sea levels, and the loss of coastal wetlands. A sharp uptick in warming in just the past decade has made the state more fire-prone and, at the same time, it has fostered the spread of the sorts of plants that provide wildfires with fuel.
Global warming causes climate change. "Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level." from IPCC, 2007: Summary for policymakers. Every single year of this century (2001-2008) has been among the top ten warmest years since instrumental records began.
Some of the major effects of warming are loss of sea ice, melting of permafrost, heatwaves and drought, frequency of wildfires (including wildfires in the tundra) -- which put more CO2 into the atmosphere and retard further absorption by plants -- reductions in food crops, hotter summers, changes in precipitation as storm systems move towards poles (leading to increases towards the poles, reductions in Mediterranean, SW North America, Southern Africa), ocean acidification, and eventually sea level rise, which will continue for centuries. Sea levels rise in a warming world for several distinct reasons: One is simple thermal expansion of ocean water (steric effects). Another is melting glaciers, and a third is the contribution from the melting of the gigantic ice sheets on Greenland and Antarctica.
Changes in the atmospheric abundance of greenhouse gases (carbon dioxide, methane, and nitrous oxide) and aerosols, as well as changes in solar radiation and in land surface properties alter the energy balance of the climate system. These changes are expressed in terms of radiative forcing, which is a measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system.
"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations" (IPCC 2007.) ("very likely" means at least 90% probable.)
The precise wording of these statements are a result of lengthy discussion between scientists and government representatives. The IPCC is both governmental and scientific. It was created not to foster new research but to compile and assess existing knowledge on a politically charged issue. Climate science does not tell us what policies to pursue, but it does identify the problems, explain why they matter, and give society insights that can help to frame efficacious policy responses.
The basic framework for treaties on Climate Change is the UNFCCC, the United Nations Framework Convention on Climate Change, which was negotiated at the "earth summit" in Rio de Janiero in 1992. Its objective was to "stabilize greenhouse gas concentration in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system". The framework set out to publish emissions information, control emissions, publish information of policies, compensate developing countries for the cost of compliance, and to transfer technologies.
As their habitats shrink and overlap, grizzlies and polar bears have started to mate, creating new hybrids: pizzlies or grolars.
The science of climate change is a complex system science and never "settled". Nonetheless, there are well-established components, as well as competing explanations and speculative components. Such a science does not work on falsification, but on preponderance of evidence. "you don't need to have every component of a problem deeply understood to practice risk management." (Steven Schneider) This confidence is "long term and global", not "short scale and local", although the most important aspects of climate change are local, not global, and are not confined to warming. The increasing awareness of rapid climate change has reduced the difference between historical time and geological time.
The science of climate change does not provide opportunities for experiment, or at least deliberate and controlled experiment — aside from humanity’s “great geophysical experiment” of increasing carbon dioxide in the atmosphere. (the quote is from Roger Revelle and Hans Seuss)
The science attempts to provide information about risk. The policies need to address risk management. (one important tenet of risk management is diversification. Flexibility is another.) There are reasonable differences of opinion of how best to respond to climate change and even how serious global warming is relative to other environmental and social issues. (Oreskes) Advocacy groups (who represent a political point of view) and media (who try to portray "balance") have different responsibilities from scientists, who consider the relative probabilities of multiple outcomes. But another question remains as well: How can we justify using science to inform policy, if the science might be wrong? (one example might be the difficulties of establishing local consequences of climate change, which are the ones that would be politically relevant) One way to address that question is to ask what evidence we have, or what other possible hypotheses could be correct.
“Climate change is a global collective action problem since all of us face the likelihood of extremely adverse outcomes that could be reduced if many participants take expensive actions.” (Elinor Ostrom) “Collective action” refers to settings where costly actions are made independently, but outcomes jointly affect everyone involved. The conventional theory predicts, for example, that no one will reduce emissions without externally imposed regulations at the global scale.
The most challenging scientific task of all is to build a common international framework for Earth System science that can harness the potential synergies that will arise from the interactions of tens of thousands of investigators, research groups and institutions around the world. The ultimate challenge, however, is directed towards the governance and management communities, as they must deal with the implications of Earth System science. How can a large group of independent nations with differing cultures, values, wealth, social organization and world views come together to manage their own single, connected life support system in a coherent and effective way? One possible strategy is polycentrism.
Extreme weather events like "Superstorm" Sandy (a hurricane that merged with with a mid-latitude weather system to form a hybrid storm) have elements of natural variability and elements of climate change. Aspects of climate change favor the odds of a stronger hurricane. Hurricanes form over warm sea surface, and surface temperatures of oceans are higher. The atmosphere is more moist, with more potential for rainfall. Storm surges during Sandy were higher because sea level is higher -- due to thermal expansion of sea water as it warms, and melting of land-based ice. While IPCC estimates are in the 18-59 cm rise by the end of the twenty-first century, a global rise of 1 meter is a plausible scenario if the Greenland and/or Antarctic ice sheets become significant sources or sea-level rise.
Climate change is also a problem about development, about access to energy, protecting poor and rural communities...(see below)
Climate refugees in Ethiopia, which has been experiencing historic droughts, that have led to water scarcity and food insecurity for millions.
In Late Victorian Holocausts Mike Davis explores the relation between climate and social critique. His basic argiument is unequivocal: the succession of devastating famines and the enduring economic marginalization of the agrarian monsoonal regions they set in train cannot be explained by either the critique of capitalism or by climatology alone. To grasp the concept of ‘the making of the Third World’ requires a fusion of critical social analysis and the geoscientific understanding of the nonlinear dynamics of the earth system.
The great challenge of the twenty-first century is to slow down climate change as much as possible. There is too much inertia in the system to stop climate change anytime soon. As the Earth’s resources become scarcer, wars and conflicts over resources seem inevitable. Today, Russia’s war on Ukraine is financed by its income from sales of hydrocarbons (oil and gas). This is a dire example of the “geohistory” that combines human history and earth history that Dipesh Chakrabarty called for. The historian Timothy Snyder calls the rulers of Russia a “hydrocarbon oligarchy”. (see his expanded version of On Tyranny.) Snyder describes the “politics of catastrophe” as a warning that “the future is coming for you.”