Query: The effect of long-term warming is to make it harder to count on snowmelt runoff in wet times

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Snow <=SEP=> Snow pertains to frozen crystalline water throughout its life cycle , starting when it precipitates from clouds and accumulates on surfaces , then metamorphoses in place , and ultimately melts , slides or sublimates away . Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air . Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets , which freeze in hexagonal-shaped crystals . Snowflakes take on a variety of shapes , basic among these are platelets , needles , columns and rime . As snow accumulates into a snowpack , it may blow into drifts . Over time , accumulated snow metamorphoses , by sintering , sublimation and freeze-thaw . Where the climate is cold enough for year-to-year accumulation , a glacier may form . Otherwise , snow typically melts seasonally , causing runoff into streams and rivers and recharging groundwater .   Major snow-prone areas include the polar regions , the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures . In the Southern Hemisphere , snow is confined primarily to mountainous areas , apart from Antarctica .   Snow affects such human activities as transportation : creating the need for keeping roadways , wings , and windows clear ; agriculture : providing water to crops and safeguarding livestock ; such sports as skiing , snowboarding , snowmachine travel ; and warfare : impairing target acquisition , degrading the performance of combatants and materiel , and impeding mobility . Snow affects ecosystems , as well , by providing an insulating layer during winter under which plants and animals are able to survive the cold .

Season creep <=SEP=> In phenology , season creep is observed changes in the timing of the seasons , such as earlier indications of spring widely observed in temperate areas across the Northern Hemisphere .  Phenological records analyzed by climate scientists have shown significant temporal trends in the observed time of seasonal events ,  from the end of the 20th century and continuing into the 21st century . In Europe , season creep has been associated with the arrival of spring moving up by approximately one week in a recent 30-year period .  Other studies have put the rate of season creep measured by plant phenology in the range of 2 -- 3 days per decade advancement in spring , and 0.3 -- 1.6 days per decade delay in autumn , over the past 30 -- 80 years .   Observable changes in nature related to season creep include birds laying their eggs earlier and buds appearing on some trees in late winter . In addition to advanced budding , flowering trees have been blooming earlier , for example the culturally important cherry blossoms in Japan ,  and Washington , D.C.  Northern hardwood forests have been trending toward leafing out sooner , and retaining their green canopies longer .  The agricultural growing season has also expanded by 10 -- 20 days over the last few decades .   The effects of season creep have been noted by non-scientists as well , including gardeners who have advanced their spring planting times ,  and experimented with plantings of less hardy warmer climate varieties of non-native plants . While summer growing seasons are expanding , winters are getting warmer and shorter , resulting in reduced winter ice cover on bodies of water ,  earlier ice-out ,  earlier melt water flows ,  and earlier spring lake level peaks .  Some spring events , or `` phenophases '' , have become intermittent or unobservable ; for example , bodies of water that once froze regularly most winters now freeze less frequently ,  and formerly migratory birds are now seen year-round in some areas .

Lake Tahoe <=SEP=> Lake Tahoe ( -LSB- ˈtɑːhoʊ -RSB- ) is a large freshwater lake in the Sierra Nevada of the United States . Lying at 6225 ft , it straddles the border between California and Nevada , west of Carson City . Lake Tahoe is the largest alpine lake in North America , and at 122160280 acre.ft trails only the five Great Lakes as the largest by volume in the United States . Its depth is 1645 ft , making it the second deepest in the United States after Crater Lake in Oregon ( 1945 ft ) .   The lake was formed about 2 million years ago as part of the Lake Tahoe Basin , with the modern extent being shaped during the ice ages . It is known for the clarity of its water and the panorama of surrounding mountains on all sides . The area surrounding the lake is also referred to as Lake Tahoe , or simply Tahoe . More than 75 % of the lake 's watershed is national forest land , comprising the Lake Tahoe Basin Management Unit of the United States Forest Service .   Lake Tahoe is a major tourist attraction in both Nevada and California . It is home to winter sports , summer outdoor recreation , and scenery enjoyed throughout the year . Snow and ski resorts are a significant part of the area 's economy and reputation . The Nevada side also offers large casinos , with highways providing year-round access to the entire area .

Global warming <=SEP=> Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .

Cryosphere <=SEP=> The cryosphere ( from the Greek κρύος kryos , `` cold '' , `` frost '' or `` ice '' and σφαῖρα sphaira , `` globe , ball '' ) is those portions of Earth 's surface where water is in solid form , including sea ice , lake ice , river ice , snow cover , glaciers , ice caps , ice sheets , and frozen ground ( which includes permafrost ) . Thus , there is a wide overlap with the hydrosphere . The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes , clouds , precipitation , hydrology , atmospheric and oceanic circulation . Through these feedback processes , the cryosphere plays a significant role in the global climate and in climate model response to global changes . The term deglaciation describes the retreat of cryospheric features . Cryology is the study of cryospheres .