It's very likely though that AGW will end up either increasing or
decreasing snow cover.
The figure 12 - B shows the Northern Hemisphere snow coverage data for each of the months since 1966 for: 6 months of the year have seen a stable or increasing snow cover, the other 6 months
a decreasing snow cover.
[1] Evidence of climate change includes the instrumental temperature record, rising sea levels, and
decreased snow cover in the Northern Hemisphere.
The point here isn't that anybody can prove that there has never been this extent of Greenland melting at some prior time in the Holocene, but that all of these indicators taken together (Arctic temperatures, low sea ice extent in summer * and * winter, permafrost melting,
decreased snow cover, Greenland melting) indicate that the Arctic as a whole really is warming in an exceptional way.
The evidence for rapid climate change is compelling: Sea level rise, Global temperature rise, Warming oceans, Shrinking ice sheets, Declining Arctic sea ice, Glacial retreat, Extreme events, Ocean acidification,
Decreased snow cover http://climate.nasa.gov/evidence/ It's changing «rapidly».
However, no anthropogenic influence can be detected for 1 - day and 3 - day surface runoff, as increases in extreme precipitation in the present - day climate are offset by
decreased snow cover and lower frozen water content in soils during the May — June transition months, compared to pre-industrial climate.
Not exact matches
«Northern Hemisphere
snow cover has
decreased and Arctic Sea ice has been at record low levels in the past three years.»
As winters arrive later and
snow melts earlier, the worldwide
decrease in
snow cover already may have dramatic impacts on animals that change coat colors with the seasons.
Decreasing spring
snow cover in the Northern Hemisphere has global consequences.
Consistent with observed changes in surface temperature, there has been an almost worldwide reduction in glacier and small ice cap (not including Antarctica and Greenland) mass and extent in the 20th century;
snow cover has
decreased in many regions of the Northern Hemisphere; sea ice extents have
decreased in the Arctic, particularly in spring and summer (Chapter 4); the oceans are warming; and sea level is rising (Chapter 5).
Since IPCC (2001) the cryosphere has undergone significant changes, such as the substantial retreat of arctic sea ice, especially in summer; the continued shrinking of mountain glaciers; the
decrease in the extent of
snow cover and seasonally frozen ground, particularly in spring; the earlier breakup of river and lake ice; and widespread thinning of antarctic ice shelves along the Amundsen Sea coast, indicating increased basal melting due to increased ocean heat fluxes in the cavities below the ice shelves.
The
decreasing trend in global
snow cover and widespread melting of glaciers is consistent with a widespread warming.
According to the recent report by the Intergovernmental Panel on Climate Change satellite data show that there are very likely to have been
decreases of about 10 % in the extent of
snow cover since the late 1960s.
[1] CO2 absorbs IR, is the main GHG, human emissions are increasing its concentration in the atmosphere, raising temperatures globally; the second GHG, water vapor, exists in equilibrium with water / ice, would precipitate out if not for the CO2, so acts as a feedback; since the oceans
cover so much of the planet, water is a large positive feedback; melting
snow and ice as the atmosphere warms
decreases albedo, another positive feedback, biased toward the poles, which gives larger polar warming than the global average;
decreasing the temperature gradient from the equator to the poles is reducing the driving forces for the jetstream; the jetstream's meanders are increasing in amplitude and slowing, just like the lower Missippi River where its driving gradient
decreases; the larger slower meanders increase the amplitude and duration of blocking highs, increasing drought and extreme temperatures — and 30,000 + Europeans and 5,000 plus Russians die, and the US corn crop, Russian wheat crop, and Aussie wildland fire protection fails — or extreme rainfall floods the US, France, Pakistan, Thailand (driving up prices for disk drives — hows that for unexpected adverse impacts from AGW?)
In the NH a lot of land surrounding the arctic ocean is subject to the combination of
decrease in seasonal
snow cover (with climate warming), and
decreasing albedo due to vegetation feedbacks.
Re 9 wili — I know of a paper suggesting, as I recall, that enhanced «backradiation» (downward radiation reaching the surface emitted by the air / clouds) contributed more to Arctic amplification specifically in the cold part of the year (just to be clear, backradiation should generally increase with any warming (aside from greenhouse feedbacks) and more so with a warming due to an increase in the greenhouse effect (including feedbacks like water vapor and, if positive, clouds, though regional changes in water vapor and clouds can go against the global trend); otherwise it was always my understanding that the albedo feedback was key (while sea ice
decreases so far have been more a summer phenomenon (when it would be warmer to begin with), the heat capacity of the sea prevents much temperature response, but there is a greater build up of heat from the albedo feedback, and this is released in the cold part of the year when ice forms later or would have formed or would have been thicker; the seasonal effect of reduced winter
snow cover decreasing at those latitudes which still recieve sunlight in the winter would not be so delayed).
As I expect kim will comment about the coming Ice Age, please note that the Arctic sea ice is at just about the same point it was this time last year; however, the area
covered by
snow in Asia has
decreased substantially.
As summer sea ice in the Arctic
decreases, the
snow / ice
cover changes to open ocean, the amount of sunlight that is reflected drops from 80 - 90 % to about 20 %.
One reason I suspect this happened is because
decreasing ice and
snow cover increased the lapse rate overall in the lowest ~ 1 - 1.5 kilometers of the lower troposphere.
Decreases also occur at high latitudes, where
snow cover diminishes (Section 10.3.3).
One of the biggest concerns is that these sudden forests will
decrease the albedo (literally «whiteness») of the tundra where
snow cover bounces solar radiation back into the atmosphere creating a cooling effect.
The 2009 State of the Climate Report of the US National Oceanic and Atmospheric Administration (NOAA) tells us that climate change is real because of rising surface air temperatures since 1880 over land and the ocean, ocean acidification, sea level rise, glaciers melting, rising specific humidity, ocean heat content increasing, sea ice retreating, glaciers diminishing, Northern Hemisphere
snow cover decreasing, and so many other lines of evidence.
Overall
snow cover has
decreased in the Northern Hemisphere, due in part to higher temperatures that shorten the time
snow spends on the ground.20
One, it makes clear that the increase in temperature is now established; the rise in temperature is the highest in the poles, where
snow and ice
cover has
decreased.
In contrast, the South and lower Midwest saw reduced snowstorm frequency during the last century.3 Overall
snow cover has
decreased in the Northern Hemisphere, due in part to higher temperatures that shorten the time
snow spends on the ground.
When the flux is increased, the planet undergoes a
decrease in surface albedo which is due to the melting of the permanent polar ice caps and the reduced seasonal
snow cover.
Based on surface temperature measurements, satellites, glacial retreat, sea level rise,
decrease in
snow -
cover in spring & fall, etc. etc..
3) The extent and duration of
snow cover and sea ice have
decreased across the Arctic.
Decrease in spring
snow cover in the Northern Hemisphere, which suggests that
snow is melting earlier than previous years
«One of the robust findings of the report is that
snow cover in most continental areas will dramatically
decrease unless warming is stopped... Large areas are expected to become
snow free.»
10 of those months showed
decrease in NH
snow cover and five were statistically significant (March, April, June, July and August).
26 Sun Stepped Art Aerosols Greenhouse gases Warming from
decrease Cooling from increase CO 2 removal by plants and soil organisms CO 2 emissions from land cleaning, fires, and decay Heat and CO 2 removal Heat and CO 2 emissions Ice and
snow cover Natural and human emissions Land and soil biotoa Long - term storage Deep ocean Shallow ocean Troposphere Fig. 20 - 6, p. 469
25 Fig. 20 - 6, p. 469 Troposphere Cooling from increase Aerosols Warming from
decrease Green - house gases CO2 removal by plants and soil organisms CO2 emissions from land clearing, fires, and decay Heat and CO2 emissions Heat and CO2 removal Deep ocean Long - term storage Land and soil biotoa Natural and human emissions Shallow ocean Sun Ice and
snow cover
[ISPM 2.2 b] This represents a marked contrast to the AR4 chapter summary which states: «
Snow cover has
decreased in most regions, especially in spring and summer.»
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring
snow cover have continued to
decrease in extent.
Bouraoui et al. (2004) showed, for southern Finland, that the observed increase in precipitation and temperature was responsible for a
decrease in
snow cover and increase in winter runoff, which resulted in an increase in modelled suspended sediment loads.
That is until the surface is
covered by
snow, which being about the same reflectivity as clouds, cancels the
decrease in the incident power so that the net effect is to trap surface warmth.
the statistically significant slope of
snow cover decrease seems to be around — 2 Mkm ^ 2 for 40 years (although Tamino doesn't give its precise value).
The video shows so many different processes at different scales, from natural processes (annual changes in
snow cover and the Vatnajökull ash plume) to climate change related changes (e.g. the long term
decrease in sea ice).
This converts to — 5 Mkm ^ 2 in 100 years, whereas the current
snow cover is around 45 Mkm ^ 2, so a
decrease of 10 % in 100 years.
All three summer months show a statistically significant
decrease, as does the combined Jun - Jul - Aug summer
snow cover.
Suppose, he said, some random
decrease of
snow cover in northern latitudes exposed dark ground.
The evidence for AGW
covers a number of areas: increases in CO2 levels, overall warming, a rise in sea levels, falls in
snow cover, receding glaciers, a
decrease in Arctic ice, earlier springs, treelines moving towards the poles.
These trends in extreme weather events are accompanied by longer - term changes as well, including surface and ocean temperature increase over recent decades,
snow and ice
cover decrease and sea level rise.
The 10 - year period ending in 2007 witnessed fewer severe cold snaps than any other 10 - year period since record keeping began in 1895.2 These changes can not be explained by natural variation, and correspond very well with computer simulations that include human influences on climate.3
Snow cover has
decreased in most regions, especially in the spring, and mountain snowpack has also
decreased in several regions.4
For example, the lower atmosphere and the upper layers of the ocean have also warmed,
snow and ice
cover are
decreasing in the Northern Hemisphere, the Greenland ice sheet is shrinking, and sea level is rising (see Figure 1b).
For example, additional evidence of a warming trend can be found in the dramatic
decrease in the extent of Arctic sea ice at its summer minimum (which occurs in September),
decrease in spring
snow cover in the Northern Hemisphere, increases in the global average upper ocean (upper 700 m or 2300 feet) heat content (shown relative to the 1955 — 2006 average), and in sea - level rise.
GMT drops initially at glacial inception in response to
decreased summer radiation at high northern latitudes that would have led to equatorward extension of sea ice and
snow cover with associated cooling from increased albedo.
Although these hydrological changes could potentially increase soil water availability in previously
snow -
covered regions during the cool low - ET season (34), this effect would likely be outweighed by the influence of warming temperatures (and
decreased runoff) during the warm high - ET season (36, 38), as well as by the increasing occurrence of consecutive years with low precipitation and high temperature (Fig. 4A).
Here's a link to Rutgers data showing that NH
snow cover did indeed
decrease just as AR5 stated.