ROCKY REX'S SCIENCE BITES

Sea level is rising , and there are several reasons connected to  global warming . An international team of researchers  has produced this graph of ocean levels, for a period of time going back to around 500 BC.  Extra water enters the sea when  ice melts  from Antarctica, Greenland and other glaciers and ice caps. Recent research suggests that  the glaciers of Alaska alone now contribute 75 gigatonnes per year. S eawater also expands  as it gets warmer, just like the liquid in a thermometer expanding as temperatures rise.  This is called 'thermal expansion.' Investigating sea level rise involves scientists using many different methods, including satellites which map the surface of the sea. It is also important to look carefully at older records from tidal gauges all over the world. Global sea level rise from the 20th century to the last two decades has speeded up even more than scientists previously thought, according to  a new Harvard study. NASA have report

Some key events in the discovery of climate change 1800-1870  Level of carbon dioxide gas (CO 2 ) in the atmosphere, as later measured in  ancient ice , was about 290 ppm (parts per million). Global temperature for 1850-1870 was about 13.6°C. 1824 Jean-Baptiste Joseph F ourier  calculated that the Earth would be far colder if it lacked an atmosphere.  1856 Eunice Foote   describes filling glass jars with water vapour, carbon dioxide and air, and comparing how much they heated up in the sun. “The highest effect of the sun’s rays I have found to be in carbonic acid gas,”    “The receiver containing the gas became itself much heated – very sensibly more so than the other – and on being removed, it was many times as long in cooling.” 1859 John Tyndall  discovered that some gases block infra-red radiation.  He suggested that  changes in the concentration of the gases  could bring  climate change . 1896  Arrhenius  published the first calculation of glob

The highly respected  Berkeley Earth  project has reported that  2016 was the warmest year in the modern record. This chart shows the  annual average global temperatures  up to 2015, from NASA's  Goddard Institute for Space Studies ( GISS ) One thing to note ….. every  La Nina   ‘year’ since 1998 was warmer than every   El Nino  ‘year’ before 1995.   It's useful to look at average global temperatures by comparing decades. This chart comes from the  World Meteorological Organisation. The high figures in the 1930s and 1940s were produced partly because there were strong El Ninos over a period from about 1939 to 1942. Since the mid 20th century global temperatures have risen, decade by decade. New research  published June 2015 confirms this trend: Over a longer term, it's obvious that the current situation is unusual. Source: Sir John Houghton A temperature rise of  2 degrees  C  above pre-industrial temperature has been agreed as a thresho

Glaciers   are melting quickly in many places. Grinnel Glacier - at the top, 1940, compared with the lower image from 2006.  Repeat photography   reveals this process. Mount Lyell is in Yosemite National Park, California. New research shows that  glacier retreat is a global phenomenon  and is "without precedent". In 2014 ,  Exit Glacier  in Alaska melted and retreated 57 metres toward the Harding ice field, which itself has lost 10 per cent of its mass since 1950. Easton Glacier in 1990, 2003 and 2015 from same location.

Average global temperature  is now higher than it has been for a long time. Graph by Klaus Bitterman. Green dots show the 30-year average of the  PAGES 2k reconstruction.   The red curve shows the global mean temperature, based on  HadCRUT4  data from 1850 onwards.  In blue is the original "hockey stick" from  a  paper by Mann, Bradley and Hughes (1999)  with its uncertainty range (light blue).  The green dots are calculated using data from many places around the world, using information from a range of  temperature proxies , such as documents, ice, lakes, pollen, tree rings, corals, seabeds and  speleothems. 78 researchers from 24 countries, together with many other colleagues, worked for seven years in the "PAGES 2k" Project  on this climate reconstruction.  Their study  is based on 511 climate archives from around the world. PAGES is the  Past Global Changes  programme launched in 1991. 

Ice cores   are cylinders of ice, drilled from an ice sheet or a glacier.  They are usually 10 centimetres in diameter, and can be taken from deep in the ice. Ice cores provide  trapped samples of ancient air . Dr Emilie Capron of the   British Antarctic Survey   said - "Air bubbles trapped in ice are like little time capsules that record the past atmospheric composition.  "So we measure loads of different gases, and essentially we can measure greenhouse gases such as carbon dioxide and methane." Most ice core records come from  Antarctica  and  Greenland. Law Dome   is a location in Antarctica. The evidence in Law Dome ice cores shows that since the 18th century, when the Industrial Revolution began, the level of carbon dioxide has risen. It has changed from around 280 parts per million to 315 ppm when Keeling began his records in 1958. Now it has reached around 400 ppm, a rise of 85 ppm in just 56 years.   The longest ice cores are f

In places which are not as frozen as they were, amazing discoveries have been made. In 1991 two hikers in the Alps found a body. They were shocked, and reported the find. It was even more extraordinary when the investigation found that the body was thousands of years old. The clothing, weapons and other items found with the body give a glimpse into life when metal was first being used. Tests later confirmed the iceman dates back to 3,300 BC. He probably died from a blow to the back of the head.  His body was so well-preserved that scientists were able to determine that his last meal was red deer, herb bread, wheat bran, roots and fruit. He lived at a time, over 5,000 years ago, when the Earth was starting to cool. So when he died high in the mountains, his body became covered with snow. Modern warming (shown by the red part of the graph) made it possible to find him.

What do scientists mean by the " Greenhouse Effect "? When the Sun's energy arrives at the Earth, it travels through the air. Some is reflected back to space, but some hits the Earth and warms it. The warm Earth gives off  infrared radiation  with various wavelengths.   Some  of those waves can pass back out of the air to space, but  some  are absorbed by certain gases in the air. The gases then re-emit the energy into the air. If there are  more  of those gases,  less  heat escapes into space. An extreme case has happened on Venus. Concentrated  'greenhouse gases'  on Venus have caused the surface temperature to rise to 735  Kelvin  (462 degrees C; around 900 degrees F) Carbon dioxide levels in the atmosphere have risen quickly  since people began burning large quantities of fossil fuels. There was carbon dioxide in the air before that, at around 270 parts per million. Without any carbon dioxide, the Earth would be ver

Carbon dioxide is always in the atmosphere as part of the Earth's  carbon cycle. The global carbon cycle transfers carbon through the Earth’s different parts -  the atmosphere, oceans, soil, plants, and animals.  So carbon moves around — it flows — from place to place. Carbon dioxide (CO 2 ) is the main  greenhouse gas  emitted through human activities.  Human activities  are changing the carbon cycle. First, by adding more CO 2  to the atmosphere, mainly by  burning fossil fuels . Also by changing the ability of  natural sinks , like forests, to remove CO 2  from the atmosphere.  Human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.   The  carbon sinks,  on land and in the oceans, have responded by increasing the amount of carbon they absorb each year. Carbon sinks cope with  about half  of human greenhouse gas emissions.  The other half has accumulated in the atmosphere.

Iceland lies on the  Mid-Atlantic Ridge , which is why it has volcanic activity. Iceland also has  ice caps  and  glaciers . Iceland is one of the fastest-warming places on the planet  – as much as four times the Northern Hemisphere average.  The glaciers that cover more than 10 percent of the island are losing an average of 11 billion tons of ice a year.                 Iceland glacial meltwater - photo Tom Harding The water melting from Iceland's glaciers would fill 50 of the world's largest trucks every minute. Parts of Iceland are rising as the ice caps melt,  reducing the weight on the Earth's crust. The thinning of the ice caps reduces the pressure on the rocks. Geologists know lower pressure from above makes volcanoes erupt more easily. Lower pressure allows volcanic gases to expand, and mantle rocks melt more easily at lower pressure as well. So more magma can rise into the volcanic systems. As that happens,  Iceland's volcanoes may get m

2016 was the warmest year in  NOAA 's 137-year series.  This is the third consecutive year a new global annual temperature record has been set.  All 16 years of the 21 st  century are included in the seventeen warmest years in the modern record (1998 is currently the eighth warmest.)  The five warmest years have all occurred since 2010. It is increasingly likely the Earth is now warmer than at any time since the Eemian Interglacial, over 115,000 years ago. The Eemian was warmer than the  Holocene  because of higher insolation. Insolation refers to the amount of solar energy received per unit time at any one location, and it was higher  due to astronomical cycles.

Atmospheric carbon dioxide concentration  is now around 400 parts per million (ppm). It last reached similar levels during the  Pliocene , 5.3-2.6 million years ago.   Outcrop of Middle Pliocene diatomaceous lake beds at Ledi Geraru, northern Afar region of Ethiopia. (photo: Roy Johnson.) In the middle Pliocene,  the concentration of carbon dioxide in the air ranged from about 380 to 450 parts per million.   During this period, the area around the North Pole was much warmer and wetter than it is now. Summer temperatures in the Arctic were around 15 degrees C , which is about 8 degrees C warmer than they are now. Global average temperatures were 2-3°C warmer than today. Sea level was up to 40 metres higher than now. Of course, there were no modern humans at that time. Hominids of the Pliocene Nor was there a  global system of food supply   relying on stable climates for agriculture.

Arctic permafrost – ground that has been frozen for many thousands of years – is now thawing because of global climate change. “The release of greenhouse gases resulting from thawing Arctic permafrost could have catastrophic global consequences,” said  Dr. Max Holmes, a Senior Scientist at the Woods Hole Research Center (WHRC). G reenhouse gas es and permafrost.   Graphic by John Garrett. Thawing permafrost releases greenhouse gases (carbon dioxide and methane) into the atmosphere, which accelerate climate change, which in turn cause more thawing of the permafrost.  This may be a fairly slow process, and there is a lot more research to be done in this area. Some scientists fear that this potentially unstoppable and self-reinforcing cycle could produce a dangerous "tipping point".

Oceania  is a region made up of thousands of  islands throughout the Central and South  Pacific Ocean.   It includes Australia, the smallest continent in terms of total land area. Many of the nations in Oceania are  Small Island Developing States (SIDS). Many scientists say that Oceania is more vulnerable than most parts of the Earth to climate change, because of its climate and geography.  The heavily coastal populations of the continent’s small islands are vulnerable to flooding and erosion  because of  sea level rise.   An international team of researchers  has produced this graph of ocean levels, for a period of time going back to around 500 BC.  Five of the Solomon Islands have been swallowed whole by rising sea levels between 1947 and 2014.  "It’s a perfect storm,” says  Simon Albert  of the University of Queensland. “There’s the background level of global sea-level rise, and then the added pressure of a natural trade wind cycle that has been physical

Heat can affect things without causing a temperature rise. Extra heat can be used in ‘ changing state ’ instead of raising temperature. A change of state could be … a  solid  melting to a  liquid .  Or a  liquid  evaporating to a  gas . So  heat is needed to change ice at zero degrees C to water at zero degrees C. And to change water into water vapour….. without raising the temperature. Scientists call the heat used to change state  latent heat. Also, there are natural variations in the global climate,  El Nino  events being the ones that affect world temperature the most. The opposite to 'El Nino' is 'La Nina', a cooling effect. If global temperatures are plotted on a graph in a way that shows these variations, it makes the overall warming trend very obvious. Every La Nina year since 1998 has been warmer than every El Nino year before 1995. As the Earth warms, each El Nino event 'rides' on a higher base-line global temperature: