Experts
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Agree
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Nobel Laureate in Physics
Agree
...by doubling the amount of CO2 ... we're doing things that have an obvious potential for producing great harm. We ought to be pretty sure we're not doing harm before we are sanguine about continuing to do these things. I really think we should control the amount of CO2 we're putting into the atmosphere, even if we're not certain.
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Politics and Business Magazine
Mostly Agree
[Our] survey will argue that although the science remains uncertain, the chances of serious consequences are high enough to make it worth spending the (not exorbitant) sums needed to try to mitigate climate change.
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Governor of California 2003-
Agree
The debate is over. We know the science. We see the threat posed by changes in our climate. And we know the time for action is now.
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Disagree
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Politics Professor, Economist, Writer
Mostly Disagree
Global warming is real and caused by CO2. The trouble is that the climate models show we can do very little about the warming. Even if everyone (including the United States) did Kyoto and stuck to it throughout the century, the change would be almost immeasurable, postponing warming by just six years in 2100. Likewise, the economic models tell us that the cost is substantial. The cost of Kyoto compliance is at least $150 billion a year.
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Geologist, President of the Geological Society of India
Mostly Disagree
There is some evidence to show that our planet Earth is becoming warmer and that human action is probably partly responsible, especially in the matter of greenhouse gas emissions. What is in doubt, however, is whether the steps that are proposed to be taken to reduce carbon emission will really bring down the carbon dioxide level in the atmosphere and whether such attempts, even carried out on a global scale, will produce the desired effect.
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Politics Professor
Disagree
The IPCC's account of things seems to me only one possibility, and the evidence for it is not very strong. For that reason, I would counsel that we accept that climate changes, and learn, as indeed human beings have learned for thousands of years, to adapt to that change as rationally and sensibly as we can.
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Arguments
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If you
disagree, then you
possibly
disagree with:
Is substantially reducing CO2 emissions worthwhile?
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Since the industrial revolution, humans have been emitting greenhouse gases that the Intergovernmental Panel on Climate Change (IPCC) believe are responsible for Global Warming. While the majority of climatologists agree with the IPCC's conclusions, skeptics suggest that the IPCC's climate models are flawed and that recent climate changes should be attributed to natural causes.
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Most of the global average warming over the past 50 years is very likely due to anthropogenic GHG increases and it is likely that there is a discernible human-induced warming averaged over each continent (except Antarctica).
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I predict that in the coming years, there will be a growing realization among the global warming research community that most of the climate change we have observed is natural, and that mankind’s role is relatively minor.
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If you
agree, then you
possibly
disagree with:
Is substantially reducing CO2 emissions worthwhile?
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For most of the last half a billion years, Earth was much hotter than it is today. However, for the past 3 million years, Earth's climate has experienced a gradually deepening ice age. Ecologists are concerned as to whether today's ecosystems can adapt to the global temperatures predicted by the IPCC, which are expected to exceed those of the warmest interglacial periods during this time.
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Animal and plant species are already being stressed by climate change. Species can migrate in response to movement of their climatic zone, but some species in polar and alpine regions will be pushed off the planet. As climate zones move farther and faster, climate change will become the primary cause of species extinction. The tipping point for life on the planet will occur when so many interdependent species are lost that ecosystems collapse.
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The oceans and coastal zones have been far warmer and colder than is projected in the present scenarios of climate change. Over millennia, marine life have endured and responded to CO2 levels well beyond anything projected, and temperature changes that put coral reefs and tropical plants closer to the poles or had much of our land covered by ice more than a mile thick.
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If you
agree, then you
possibly
disagree with:
Is substantially reducing CO2 emissions worthwhile?
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Climate engineering is the idea of deliberately modifying earth's atmosphere, such as by adding gases that reflect sunlight. Its appeal is that it may be a cheaper and faster way to combat climate change than reducing CO2 emissions. Its stronger advocates suggest it may even be the only solution to climate change, given the amount of CO2 already in the atmosphere and negative political-economic realities. Skeptics worry that tinkering with the atmosphere may lead to unforeseen consequences.
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The so-called geoengineering approaches are really only a last resort, because all of them have potentially harmful environmental side effects, such as additional ozone depletion, and we're not at the point yet where we're desperate.
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Given the grossly disappointing international political response to the required greenhouse gas emissions, ...research on the feasibility and environmental consequences of climate engineering of the kind presented in this paper, which might need to be deployed in future, should not be tabooed. ...the possibility of the albedo enhancement scheme should not be used to justify inadequate climate policies but merely to create a possibility to combat potentially drastic climate heating.
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Indirect Arguments
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If you
disagree, then you
presumably
disagree with:
Is global warming caused primarily by humans?
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In 1896 Svante Arrhenius modeled the greenhouse effect, where gases in the atmosphere such as CO2 trap sunlight much like glass traps heat in a greenhouse. His principle is foundational in climatology, though today we have a more refined understanding of physical chemistry and we use Global Climate Models to predict that an increase in CO2 will actually result in global warming.
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It is very likely that glacial-interglacial CO2 variations have strongly amplified climate variations, but it is unlikely that CO2 variations have triggered the end of
glacial periods. Antarctic temperature started to rise several centuries before atmospheric CO2 during past glacial terminations.
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CO2 increases may accompany temperature increases rather than causing them. Indeed, some high resolution studies have suggested that the temperature increases precede the CO2 increases. Interestingly, also, ice core data shows strong temporal correlations between inferred temp. and amount of dust preserved in the ice core. Finally, the older geological record shows several dramatic examples of where CO2 concentration and global average temperature were either unrelated or even anti-correlated.
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If you
agree, then you
possibly
disagree with:
Is global warming caused primarily by humans?
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The intensity of the Sun is one of many input parameters used in climate models. None of the models used by the IPCC are able to successfully reproduce recent global temperature changes as a function of solar activity without also factoring in human greenhouse emissions. Some skeptics have suggested that this may be because of unknown complex feedbacks in Earth's climate.
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The TAR [Third Assessment Report] states that the changes in solar irradiance are not the major cause of the temperature changes in the second half of the 20th century unless those changes can induce unknown large feedbacks in the climate system.
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By the mid-21st century the planet will face another Little Ice Age, similar to the Maunder Minimum, because the amount of solar radiation hitting the Earth has been constantly decreasing since the 1990s and will reach its minimum approximately in 2041.
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If you
agree, then you
possibly
disagree with:
Is global warming caused primarily by humans?
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Oscillations in earth's orbit called Milankovitch cycles are at least partly responsible for climate change over tens and hundreds of thousands of years. However, the IPCC does not believe this is the cause of global warming over the last century.
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It is virtually certain that global temperatures during coming centuries will not be significantly influenced by a natural orbitally induced cooling. It is very unlikely that the Earth would naturally enter another ice age for at least 30 kyr.
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The accelerating warming of the Earth is not caused by man but by the regularities of the planets' circulation around the Sun.
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If you
agree, then you
possibly
disagree with:
Is global warming caused primarily by humans?
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Earth's atmosphere is bombarded by high energy particles from other galaxies called cosmic rays. An interesting theory is that when these particles hit Earth, they help form the type of clouds that reflect sunlight back into space, cooling the atmosphere. Since we know that the Sun forms a shield limiting the amount of cosmic radiation hitting the earth, the theory would imply that when the Sun is stronger, we'd have less cooling clouds, making the atmosphere hotter.
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I think that as a factor in climate change, it's pretty clear that we don't have any indication at this point that [cosmic rays] are important at all.
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[Sun and cosmic rays] will probably be able to account for somewhere between a half and the whole of the increase in the Earth's temperature that we have seen in the last century.
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If you
disagree, then you
possibly
disagree with:
Is global warming caused primarily by humans?
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The equilibrium of Earth's climate is a balancing act between the heating effect of the sun countered by the cooling effect of radiation from earth sent back into space. Earth's rich atmosphere and diverse surface complicates this equation with effects such as the greenhouse effect (the trapping of heat), giving rise to the study of climatology. The IPCC believes we understand this system well enough to predict it, at least in terms of global averages over decadal time periods.
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What the IPCC produces is not based on two years of literature, but 30 or 40 years of literature. We're not dealing with short-term weather changes, we're talking about major changes in our climate system. I refuse to accept that a few papers are in any way going to influence the long-term projections the IPCC has come up with.
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Our imperfect understanding of the causes and consequences of climate change means the science is far from settled.
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If you
agree, then you
presumably
agree with:
Is global warming caused primarily by humans?
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The IPCC (Intergovernmental Panel on Climate Change) is a scientific body formed by the United Nations in 1988 to summarize research on climate change for the purpose of informing policy makers. Those who are skeptical of anthropogenic global warming have questioned the objectivity of the organization.
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The IPCC produces key scientific material that is of the highest relevance to policymaking, and is agreed word-by-word by all governments, from the most skeptical to the most confident. This difficult process is made possible by the tremendous strength of the underlying scientific and technical material included in the IPCC reports.
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The disappearance of the IPCC in disgrace is not only desirable but inevitable. The reason is, that the world will slowly realise that the "predictions" emanating from the IPCC will not happen. The absence of any "global warming" for the past eight years is just the beginning. Sooner or later all of us will come to realise that this organisation, and the thinking behind it, is phony. Unfortunately severe economic damage is likely to be done by its influence before that happens.
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If you
agree, then you
possibly
disagree with:
Can life adapt to a warmer earth?
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The IPCC's Global Climate Models (GCMs) predict that hotter climates will have more extreme weather patterns, such as hurricanes.
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The type, frequency and intensity of extreme events are expected to change as Earth’s climate changes, and these changes could occur even with relatively small mean climate changes. Changes in some types of extreme events have already been observed, for example, increases in the frequency and intensity of heat waves and heavy precipitation events.
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A new technique for deriving hurricane climatologies from global data, applied to climate models, indicates that global warming should reduce the global frequency of hurricanes, though their intensity may increase in some locations.
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If you
agree, then you
presumably
disagree with:
Can life adapt to a warmer earth?
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Over the last million years, Earth's sea level has lowered during ice ages - it was 140 meters lower 18,000 years ago; and elevated during interglacials - it was 6 meters higher 125,000 years ago. The sea level would again rise to that 6 meter high if the Greenland ice melted, which would be devastating for coastal populations. Some skeptics don't believe that there will be a substantial net reduction in the world's ice, even if temperatures increase as the IPCC predicts.
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West Antarctic and Greenland ice sheets are vulnerable to even small additional warming. These two-mile-thick behemoths respond slowly at first, but if disintegration gets well under way, it will become unstoppable. Debate among scientists is only about how much sea level would rise by a given date. In my opinion, if emissions follow a business-as-usual scenario, sea level rise of at least two meters is likely within a century. Hundreds of millions of people would become refugees...
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If Arctic ice should melt, the sea level will not change because the volume of water created by melting ice is equal to the volume of water that ice displaces when floating.... A rise of 3-6 degrees Celsius over the next century promised by pessimists could not have a significant influence on the Antarctic, where the av. temperature is less than -40 C.
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Comments
Collective
Agree
The fact that global warming is real is no longer a debate. We must reduce CO2 emissions, otherwise it's doom. It's as simple as that.
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Disagree
OK, let's assume global warming is caused by humans. A big assumption, but let's assume that.
How is reducing emissions the most effective way? The world economy is a carbon based economy. It's far too expensive right now to switch. We need to think smart. Geoengineering is the way to go. For less than 1% of the cost, we can reduce the greenhouse effect by putting dust into space, mirrors into space, whatever.
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