Podnebne spremembe pomenijo dni se daljša, znanstveniki ugotovili,

Climate change means days are getting longer, scientists find

 

Powered by guardian.co.ukTa članek z naslovom “Podnebne spremembe pomenijo dni se daljša, znanstveniki ugotovili,” je napisal Oliver Milman, za theguardian.com v petek, 11. decembra 2015 19.00 UTC

Vpliv podnebnih sprememb se lahko zdi, da so večinoma negativni, vendar pa je svetla točka za tiste, ki se borijo, da bi našli dovolj časa na dan: taljenje ledenikov povzroča vrtenje Zemlje, da počasi s tem podaljšamo naše dni, Nova raziskava je pokazala,.

Harvard University raziskovalci so zagotovili odgovor na daljši potekal uganka nad tem, kako krčenje ledenikov vplivajo na vrtenje in os Zemlje, izračun, da je trajanje dan podaljšala s milisekundo v preteklosti 100 let.

Zavore se bodo še ostreje uporablja za vrtenje Zemlje kot topijo ledeniki na vedno hitreje, kar pomeni, da se bo vsaj pet milisekund doda vsak dan tekom 21. stoletja. Os Zemlje bo premik preveč, z severni pol naj bi premaknili za približno 1 cm (o.4in) v tem stoletju.

raziskava, objavljeno v znanosti predujmi, očitno rešili znanstveno sestavljanko znan kot "Munk je enigma", ki je prišel iz 2002 raziskovalec papir, ki ga oceanograf Walter Munk, preučuje, kako je taljenje ledenikov spremenila Zemljino rotacijo in os.

Kot zemljišča led na polih topi zaradi naraščajočih atmosferske temperature, prestavno teža vode po vsem svetu naj bi povzročila spremembo os, na kateri se Zemlja vrti, in rahlo tresenje v rotaciji. Prav tako, dodana teža vode proti ekvatorju bo povzročila Zemlja počasi, veliko na poti predenje drsalka bi upočasnilo, če on ali ona dosegla svoje roke ločeno od svojega telesa.

Munk vključeno v vplivu na koncu ledene dobe 5,000 pred leti, pri taljenju več kot prejšnji 15,000 let, ki bi pomagala upočasniti Zemljino rotacijo. Vendar, presenetljivo, je ugotovil, da se je povprečna gladina morja tudi s dvigne 2mm leto v 20. stoletju, ni prišlo do spremembe v rotaciji ali os Zemlje poleg tistih, ki ledeni dobi, ki se konča povzročajo.

"Treba bi jih bilo nekaj velikega velik signal, in da bi bilo takojšnje, saj traja le nekaj dni ali tednov za tem stopljene vode iz poloma premik po vsem svetu,"Je povedal Jerry Mitrovica, professor of geophysics at Harvard University and leader of the research.

Mitrovica’s team went back to Munk’s research and applied the latest scientific understanding to it. They found that Munk had slightly overestimated the average sea level rise – it was around 1mm to 1.5mm each year over the 20th century rather than 2mm.

They also applied an updated model to the calculations. Munk assumed the Earth had rapidly adjusted to ice melting that occurred as the Ice Age ended. More recent understanding of this time, vseeno, suggests that the Earth was not as spherical as it is now for a long time, as the huge ice sheets caused the poles to flatten and the equator to bulge out.

Once the team had factored in other influences such as the tides, they found that the glacier melting of the 20th century had indeed caused the Earth to slow and wobble. The speed of the planet’s rotation can be gauged from measurements of stars’ position in relation to Earth and also the orbit of satellites, which have to adjust slightly if the world’s rotation changes.

This slowdown is set to become more pronounced. The global average sea level rise is now over 3mm, according to the IPCC, with the volume of the world’s glaciers set to slump by between 15% in 85% jo 2100, depending on how sharply nations reduce greenhouse gas emissions and reverse mass deforestation.

A recent study found that the current retreat of the world’s glaciers was “historically unprecedented”, with scientists warning that a huge glacier in Grenlandija that holds enough water to raise global sea levels by half a meter has begun to crumble into the North Atlantic Ocean. Sea level rise is also fuelled by thermal expansion, where the ocean grows as it warms up.

“The period of a day is now a millisecond longer than a century ago but that will accelerate as the melting increases,” Mitrovica said. “People won’t be running from their houses screaming about an extra millisecond but it adds yet further confirmation of what we are doing to our environment. It’s another fingerprint.”

guardian.co.uk © Guardian News & Media Limited 2010