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| | | Climate Change |
Maintained by WMO |
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| | Natural or man-made? | | | | Human activities are increasing the atmospheric concentrations of greenhouse gases (which tend to warm the atmosphere) and, in some regions, aerosols (which tend to cool the atmosphere). These changes in greenhouse gases and aerosols, taken together, are projected to lead to regional and global changes in climate and climate-related parameters such as temperature, precipitation, soil moisture and sea level. Based on the range of sensitivities of climate to increases in greenhouse gas concentrations reported by the Intergovernmental Panel on Climate Change (IPCC) and plausible ranges of emissions and aerosol concentrations, climate models project an increase in global mean surface temperature. For the next two decades a warming of about 0.2°C per decade is projected and an associated increase in sea level of about 18-59 cm. The reliability of regional-scale predictions is still low and the degree to which climate variability may change is uncertain. However, potentially serious changes have been identified, including an increase in some regions in the incidence of extreme high-temperature events, floods and droughts, with resultant consequences for fires, pest outbreaks, and ecosystem composition, structure and functioning, including primary productivity. The 2007 IPCC report uses data from various sources, such as in the figure to estimate a temperature increase from 1850-2005 of 0.76 C (1.4 F) | | | | Adapting to the consequences | | |  Policymakers will have to decide to what degree they want to take precautionary measures by mitigating greenhouse gas emissions and enhancing the resilience of vulnerable systems by means of adaptation. Uncertainty does not mean that a nation or the world community cannot position itself better to cope with the broad range of possible climate changes or protect against potentially costly future outcomes. Delaying such measures may leave a nation or the world poorly prepared to deal with adverse changes and may increase the possibility of irreversible or very costly consequences. Options for adapting to change or mitigating change that can be justified for other reasons today (e.g., abatement of air and water pollution) and make society more flexible or resilient to anticipated adverse effects of climate change appear particularly desirable. (Image courtesy of FAO/G Bizzarri.) | | | | Was the Earth Warmer Before? Sea Level Higher? CO2 Higher? | | | IPCC: Global average sea level in the last interglacial period (about 125,000 years ago) was likely 4 to 6 m higher than during the 20th century, mainly due to the retreat of polar ice. Ice core data indicate that average polar temperatures at that time were 3 to 5°C higher than present, because of differences in the Earth’s orbit. The Greenland ice sheet and other Arctic ice fields likely contributed no more than 4 m of the observed sea level rise. There may also have been a contribution from Antarctica (IPCC SPM 2007).
NOAA: The Mid-Cretaceous period is one period in the geologic past that stands out as distinctly warmer than today, particularly at high latitudes. During the mid-Cretaceous Period, 120-90 million years ago, fossil remains of plants and animals believed to inhabit warm environments, were found at much higher latitudes. Breadfruit trees apparently grew as far north as Greenland (55° N), and in the oceans, warm water corals grew farther away from the equator in both hemispheres....... The mid-Cretaceous was characterized by geography and an ocean circulation that was vastly different from today; as well as higher carbon dioxide levels (at least 2 to 4 times higher than today). This indicates that the mid-Cretaceous climate system was different from that of today or any we might have in the future. Explanations evoking ocean and atmospheric circulation patterns radically different from today have been proposed to explain the climate of the mid-Cretaceous; however, there is no scientific consensus on how the Mid-Cretaceous warm climate came about. Source: NOAA Paleo Climatology program. | | | | How Significant is the Risk to the Oceans? | | | The oceans and coastal zones have been far warmer and colder than is projected in the present scenarios of climate change. Marine life has been in the oceans nearly since when they were formed. During the millennia they endured and responded to CO2 levels well beyond anything projected, and temperature changes that put tropical plants at the poles or had much of our land covered by ice more than a mile thick. The memory of these events is built into the genetic plasticity of the species on this planet. IPCC forecasts are for warming to occur faster than evolution is considered to occur, so impacts will be determined by this plasticity and the resiliency of affected organisms to find suitable habitats. In the oceans, major climate warming and cooling is a fact of life, whether it is over a few years as in an El Niño or over decades as in the Pacific Decadal Oscillation or the North Atlantic Oscillation. Currents, temperatures, salinity, and biology changes rapidly to the new state in months or a couple years. These changes far exceed the changes expected with global warming and occur much faster. The one degree F. rise since 1860 is virtually noise in this rapidly changing system. Sea level has been inexorably rising since the last glaciation lost its grip a mere 10,000 years ago. It is only some few thousand years since trees grew on Georges Bank and oysters flourished on its shores. Their remains still come up in dredges and trawls in now deep water, with the oysters looking like they were shucked yesterday. In the face of all these natural changes, and possible anthropogenic changes, some species flourish while others diminish. (Source: Statement of Dr. John Everett.)
Nevertheless, we must all be prudent in modifying our activities so that we are good stewards of our environment. There could always be unexpected consequences, and the worst case IPCC scenarios are possible, otherwise they would not be on the table for consideration. | | | | |
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| Scientists Discuss Climate Change at World Ocean Conference
by Honorine, Solenn, VOA News 12 May 2009 | |
| | Scientists and politicians have gathered in the Indonesian city of Manado for the World Ocean Conference. They are discussing the role of oceans in mitigating climate change and how climate change affects the world's seas, but their efforts are hampered by a lack of knowledge about the oceans. | |
Read more at http://www.voanews.com/e ... voa12.cfm.
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