New study independently confirms the world's oceans are warming
Rising temperatures can be charted back to the late 1950s, and the last five years were the five hottest on record
Why greenhouse gases heat the ocean
NOAA: Global Ocean Heat and Salt Content
Scientists have long known that more than 90 percent of the heat energy from man-made global warming goes into the world’s oceans instead of the ground. And they’ve seen ocean heat content rise in recent years. But the new study, using ocean-observing data that goes back to the British research ship Challenger in the 1870s and including high-tech modern underwater monitors and computer models, tracked how much man-made heat has been buried in the oceans in the past 150 years. The world’s oceans absorbed approximately 150 zettajoules of energy from 1865 to 1997, and then absorbed about another 150 in the next 18 years, according to a study published Monday in the journal Nature Climate Change.
“Til nå har klimaforskere trodd at opptaket av menneskeskapte CO2-utslipp blir jevnt fordelt mellom atmosfære, hav og vegetasjon. Nye og omfattende målinger fra Nord-Atlanteren viser at dette ikke er tilfelle.– CO2 -konsentrasjonen i havoverflaten øker raskere enn i atmosfæren", sier Truls Johannessen ved Geofysisk institutt, UiB.”
Ser du på varmeinnholdet i havet, øker dette i betydelig grad, se figur 1 og 2 her: Dette er en viktig faktor for at globalt havnivå stiger.
As Earth warms, much of the extra heat is stored in the planet’s ocean – but monitoring the magnitude of that heat content is a difficult task. A surprising feature of the tides could help, however. Scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, are developing a new way to use satellite observations of magnetic fields to measure heat stored in the ocean.
Researchers for the first time have identified the detection of sea level “fingerprints”: detectable patterns of sea level variability around the world resulting from changes in Earth’s ice. The new research will aid in sea level projections. As ice sheets and glaciers undergo climate-related melting, certain regions are hit harder, and Greenland and Antarctica contribute differently to the process. For instance, sea level rise in California and Florida generated by the melting of the Antarctic ice sheet is up to 52 percent greater than its average effect on the rest of the world.
Observed and simulated full-depth ocean heat-content changes for 1970–2005 (Lijing Cheng et al 2016)
Greenhouse-gas emissions have created a planetary energy imbalance that is primarily manifested by increasing ocean heat content (OHC).
Not only does the climate model-based study, Meehl (2011), show heat is buried into deeper ocean layers when global surface temperatures stall, but it also presents plausible mechanisms in ocean circulation that transport heat down to the deep ocean. The general pattern of sea surface temperature during these hiatus periods is very reminiscent of a La Niña-like climate state. Meehl (2011) is also climate modeling-based study, which finds that decade-long periods of little or no warming are relatively common in the model simulations. This helps to explain why global warming is not a steadily rising, or monotonic trend, consistent with the temperature observations to date.
Figure 1 - Ocean heat content (0-700 mtrs) for the period 1955 to 2008. Adapted from Levitus (2009). Two periods of ocean warming hiatus highlighted in blue. Both periods exceed 10 years in length. This see-sawing of upper ocean heat is simply part of the natural variability inherent in the climate, which occurs even during periods where the ocean is experiencing long-term warming. During these "hiatus" periods the surface layers of the ocean undergo little or no warming, but the ocean below undergoes substantial warming.
Reconciling controversies about the ‘global warming hiatus’
Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the ‘global warming hiatus’, caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of ‘hiatus’ and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.
Sea level fluctuations during El Niño (rising) and La Niña (falling) are the result of large exchanges of water between land and ocean in the form of rain and snow. This averages out to zero over time. It does not affect long-term sea level rise, which comes from melting icesheets, glaciers, and thermal expansion.
Varmere hav holder mindre oksygen. Og havene varmes raskt; 90% av global oppvarming foregår i havene. Det er lite oksygen i dypet allerede, og jo varmere det blir, jo høyere opp flytter de ulike oksygennivåene seg. D.v.s. at fisk og dyr som tilpasser seg et spesielt oksygennivå (som de aller fleste av dem gjør) også flytter seg oppover, og fortrenger det som alt var der (videre oppover). https://www.dagbladet.no/nyheter/dette-bildet-bekymrer-forskerne-havene-er-fulle-av-dode-soner/69389820
Scientists predicted in the 1980s that a key fingerprint of anthropogenic climate change would be found in the ocean. If they were correct that increases in greenhouse gases were changing how much heat was coming into the system, then the component with the biggest heat capacity, the oceans, is where most of that heat would end up.
Satellite measurements tell us that over the past century, the Global Mean Sea Level (GMSL) has risen by 4 to 8 inches (10 to 20 centimeters). However, the annual rate of rise over the past 20 years has been 0.13 inches (3.2 millimeters) a year, roughly twice the average speed of the preceding 80 years.Over the past century, the burning of fossil fuels and other human related activity and natural activities has released enormous amounts of heat-trapping gases into the atmosphere. These emissions have caused the Earth's surface temperature to rise, and the oceans absorb about 80 percent of this additional heat.The rise in sea levels is linked to three primary factors, all induced by this ongoing global climate change.
- Thermal Expansion: When water heats up, it expands. About half of the past century's rise in sea level is attributable to warmer oceans simply occupying more space.
- Melting Glaciers and Polar Ice Caps: Large ice formations, like glaciers and the polar ice caps, naturally melt back a bit each summer. In the winter, snows, primarily from evaporated seawater, are generally sufficient to balance out the melting. Recently, though, persistently higher temperatures caused by global warming have led to greater than average summer melting as well as diminished snowfall due to later winters and earlier springs. This imbalance results in a significant net gain in the ratio of runoff to ocean evaporation, causing sea levels to rise.
- Ice Loss from Greenland and West Antarctica: As
with the glaciers and ice caps, increased heat is causing the massive
ice sheets that cover Greenland and Antarctica to melt at an accelerated
pace. Scientists also believe melt water from above and seawater from
below is seeping beneath Greenland's and West Antarctica's ice sheets,
effectively lubricating ice streams and causing them to move more
quickly into the sea. Higher sea temperatures are causing the massive
ice shelves that extend out from Antarctica to melt from below, weaken,
and break off.
Apart from the above there is evidence that this has happened before in the Earths cycle but this was kept in check due to no human interference making things far worse.
Sea levels stabilized around 4,000 years ago. From Shakun 2015:
The rate of global sea level rise has been accelerating in recent decades, rather than increasing steadily, according to a new study based on 25 years of NASA and European satellite data. The new research suggests he world’s oceans will be on average at least 60cm higher by the end of the century.
Sea level rise is happening now, and the rate at which it is rising is increasing every year, according to a study released Monday in the Proceedings of the National Academy of Sciences.
Researchers, led by University of Colorado-Boulder professor of aerospace engineering sciences Steve Nerem, used satellite data dating to 1993 to observe the levels of the world's oceans.Using satellite data rather than tide-gauge data that is normally used to measure sea levels allows for more precise estimates of global sea level, since it provides measurements of the open ocean.
- Brandon Miller, CNN, Feb 12, 2017
There was a huge climate report out just now from the USA:
The report was peer reviewed by the National Academy of Sciences.You know, the academy founded by Abraham Lincoln.They have 200 Nobel Prize winners among their members.
Global mean sea level (GMSL) has risen by about 7–8 inches (about 16–21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993 (very high confidence). Human-caused climate change has made a substantial contribution to GMSL rise since 1900 (high confidence).
Slangen et al 2016, Human activities are the dominant contribution to SLR since 1970. Anthropogenic forcing dominates global mean sea-level rise since 1970 "the anthropogenic forcing (primarily a balance between a positive sea-level contribution from GHGs and a partially offsetting component from anthropogenic aerosols) explains only 15 ± 55% of the observations before 1950, but increases to become the dominant contribution to sea-level rise after 1970 (69 ± 31%), reaching 72 ± 39% in 2000 (37 ± 38% over the period 1900–2005)"
1. Although natural variations in radiative forcing affect decadal trends, they have little effect over the twentieth century as a whole
2. In 1900, sea level was not in equilibrium with the twentieth-century climate, and there is a continuing, but diminishing, contribution to sea-level change from this historic variability
3. The anthropogenic contribution increases during the twentieth century, and becomes the dominant contribution by the end of the century. Our twentieth-century number of 37 ± 38% confirms the anthropogenic lower limit of 45%
4. Our results clearly show that the anthropogenic influence is not just present in some of the individual contributors to sea-level change, but actually dominates total sea-level change after 1970
Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous.
NASA følger havnivået her
The rise in sea levels seen over the past century is unmatched by any period in the past 6,000 years, according to a lengthy analysis of historical sea level trends.Anthropogenic forcing dominates global mean sea-level rise since 1970.
The reconstruction of 35,000 years of sea level fluctuations finds that there is no evidence that levels changed by more than 20cm in a relatively steady period that lasted between 6,000 years ago and about 150 years ago. This makes the past century extremely unusual in the historical record, with about a 20cm rise in global sea levels since the start of the 20th century. Scientists have identified rising temperatures, which have caused polar ice to melt and thermal expansion of the sea, as a primary cause of the sea level increase.
A two-decade-long collection of about 1,000 ancient sediment samples off Britain, north America, Greenland and the Seychelles formed the basis of the research, led by the Australian National University and published in PNAS.
Det er ingen "pause" i oppvarming som uttrykkes i form av havnivåstigningen. Havnivået stiger fordi varmere vann utvider seg og trenger mer plass, og fordi vannet fra is som smelter (på Grønland og Antarktis) er med på å øke volumet. Havet tar til seg mesteparten av den ekstra varmen som den økte drivhuseffekten skaper.
Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers and the expansion of sea water as it warms. The first graph tracks the change in sea level since 1993 as observed by satellites.
The most respected reconstruction of global sea level during that time based on the global network of tide gauges is from Church & White:
A plot of the PSMSL tide-gauge station data aggregated into a GMSL data set by Church & White . There are significant changepoints at around 1934 and 2000, with the slope of the most recent segment being 4.1 mm/yr. (This is fairly consistent with Yi et al. 2015 , which finds that since 2010 global mean sea level "has been rising at a rate of 4.4 ± 0.5mm/yr for more than 3 years, due to an increase in the rate of both land ice loss and steric change.") Since there's a temporal increase in the rate of SLR for each segment, SLR is accelerating in this data set.
1. Church JA and White NJ: Sea-level rise from the late 19th to the early 21st century. Surveys in Geophysics 32(4–5):585–602, 2011. dx.doi.org/10.1007/s10712-011-9119-1
2. Yi S, Sun W, Heki K, Qian A: An increase in the rate of global mean sea level rise since 2010. Geophysical Research Letters 42(10):3998–4006, 2015. dx.doi.org/10.1002/2015GL063902
Huge Arctic report ups estimates of sea-level riseThe Arctic is warming more than twice as fast as the rest of the planet, suggests a huge assessment of the region. The warming is hastening the melting of Arctic ice and boosting sea-level rise.
Sea level rise isn’t just happening, it’s getting faster. Se rapporten her.
For ordens skyld; havnivået kan variere regionalt/lokalt"
Sea level rise at specific locations may be more or less than the global average due to local factors: subsidence, upstream flood control, erosion, regional ocean currents, and whether the land is still rebounding from the compressive weight of Ice Age glaciers."
FAQ 13.1 | Why Does Local Sea Level Change Differ from the Global Average? Shifting surface winds, the expansion of warming ocean water, and the addition of melting ice can alter ocean currents which, in turn, lead to changes in sea level that vary from place to place. Past and present variations in the distribution of land ice affect the shape and gravitational field of the Earth, which also cause regional fluctuations in sea level. Additional variations in sea level are caused by the influence of more localized processes such as sediment compaction and tectonics.
In terms of the Maldives and sea level rise, it is nevertheless a bit special, and about how much dry land there is; no direct consequence of the sea level. Since the islands consist largely of coral, what goes too far up the sea will weather and erode away if the sea is sinking / the land rises, and when the sea rises / the land is sinking, the corals will grow and "fill up". So in the long run, such islands will be "just above sea level". The problem is if the water rises "too fast" and "we" at the same time have built cities and roads and airports and so on.
There is nothing in this study which is new nor in conflict with AGW theory or sea level rise.
Its all old news. Science have good understanding about atoll islands. Its science in progress.
Small atoll islands may grow, not sink, as sea levels rise:
Atoll islands are more dynamic then we realized....it seems. They don't disprove sea rise, but it does broaden our thinking about how sea rise.
Havet blir surere.
Verdenshavene blir surere. De siste 200 årene har gjennomsnittlig surhet i havoverflaten økt med 26 prosent på verdensbasis, og Arktis er spesielt utsatt for forsuring. Norske havområder er spesielt utsatt for havforsuring, særlig lengst i nord.
Årsaken er blant annet at kaldt vann kan ta opp mer CO2 enn varmere vann, og at tilførsler av ferskvann fra elver og issmelting svekker havets evne til å nøytralisere forsuringen. Pågående klimaendringer i form av økt nedbør, økt avrenning med elver og økt issmelting, vil i tillegg kunne forsterke sårbarheten og ytterligere redusere havets motstandskraft mot forsuring.
Mer CO2 i norske havområder enn før. Overvåking av pH og oppløst CO2 i norske havområder viser at innholdet av CO2 øker. Dette skyldes at de menneskeskapte utslippene av CO2 har økt, og at det er mer CO2 i atmosfæren enn tidligere. Det antas at havet hittil har tatt opp 50 prosent av alle menneskeskapte CO2-utslipp. På grunn av forsuringen er havets evne til å ta opp CO2 redusert, så i dag regner en at havet tar opp 25 prosent av de menneskeskapte utslippene.
Tilbake til den store rapporten som var peer reviewed av the National Academy of Sciences.
Fourth National Climate Assessment (NCA4), Volume I
The world’s oceans are currently absorbing more than a quarter of the CO2 emitted to the atmosphere annually from human activities, making them more acidic (very high confidence)