ROCKY REX'S SCIENCE BITES

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) - this is not going to happen on Earth. 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. ...

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 ga...

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.            Guides work to build a new bridge across a river draining from Falljokull glacier ahead of the summer season when meltwater run-off increases [Alexander Lerche/Al Jazeera] 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 allow...

Atmospheric carbon dioxide concentration  is now over 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. For more on research into the climate...

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 add...

The constellation of  Orion  dominates the southern part of the sky during winter evenings in the Northern Hemisphere. The brightest stars of Orion have wonderful names. The Red Giant star  Betelgeuse  marks one shoulder, the other shoulder is marked by  Bellatrix . The three Belt Stars (left to right) are  Alnitak ,  Alnilam  and  Mintaka. The knees are marked by  Saiph  and the very bright  Rigel . Like many star names, they are of Arabic origin . The stars of Orion act as signposts to other stars seen at the same time of year. Orion's stars are good examples of some of the wide variety of types of stars.   The Sun is really rather small compared to many stars

Eucla, in south-east Western Australia, hit 49.8 degrees Celsius on December 19th, 2019. The map shows Australia coloured dark red, indicating temperatures around 40°C. However, some spots of the country are covered with white spots, indicating the heat was inching towards 50°C. Leading climate scientist Stefan Rahmstorf said..... "the probability for this extreme heat occurring by chance in a world without global heating is essentially zero. " Huge bushfires  have swept through many areas, destroying homes and wildlife. Another leading climate scientist, Michael Mann, said ... "Yes -we might have still seen an Australian heat wave, but we wouldn't have seen such a RECORD early summer heatwave in the absence of human-caused planetary warming..."

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 ba...

Summer in the southern hemisphere, winter in the northern hemisphere. Seasons are caused by the tilt in the Earth's axis. Winter Solstice is the time of the longest night and shortest day. Many ancient monuments are lined up with the solstice, which suggests it was an important moment of the year for many cultures. One is  Maeshowe  on Orkney. Others include  Stonehenge  and  Newgrange . Winter solstice sunset at Stonehenge in the mid-1980s. Image via Wikimedia Commons. Archaeologists have found evidence that p rehistoric people brought animals to  Stonehenge  from as far as north-east Scotland, to take part in midwinter feasts and ceremonies. One of the key researchers who has made a special study of Stonehenge in recent years is  Professor Mike Parker Pearson. He has written a number of academic papers and books on these recent discoveries.

Deltas  often form when rivers reach the sea. The river can carry sand and mud when it is flowing fast. As the water enters the sea, it s lows down , and the sediment drops to make the delta. Many deltas are at risk from climate change.   This map shows the levels of risk. Many deltas are at risk from climate change.   This map shows the levels of risk. An estimated 80 percent of the world's megacities are located in fragile river deltas.   A megacity has a population of over 10 million people. Over 500 million people live on deltas. Why are deltas at risk? One reason  is  rising sea level , which wears away the delta from the front. Deltas are an example of the complex processes that happen along coastlines.

An  international research project  has found human activity has been causing global warming for almost two centuries,  according to a report in Phys.Org Australian National University researcher Associate Professor Nerilie Abram. Credit: Stuart Hay, ANU Lead researcher Associate Professor Nerilie Abram from The Australian National University (ANU) said that their study found that warming began during the early stages of the Industrial Revolution. Warming is first detectable in the Arctic and tropical oceans around the 1830s, much earlier than scientists had expected. CO2 information from ice cores shows that atmospheric CO2 levels began to rise from around 280 ppm as the 19th century began. Atmospheric CO 2  concentration over the last millennium, as reconstructed from ice core data obtained by  Etheridge  et al . (1998)  at  Law Dome , Antarctica.

When the last glacial period ended about 11,500 years ago, the Earth's modern climate began to develop.  The large continental ice sheets shrank, and sea level rose. Around 8,200 years ago, however, a major cooling event occurred.  The   8.2 ka event   was first discovered in the Greenland ice core  GISP2. Over two decades temperature cooled about 3.3°C in Greenland . Temperatures in Europe dropped by around 2 °C. The entire event lasted about 150 years. Then temperatures warmed, returning to their previous levels.  So what caused the 8.2 ka event? As the large ice sheets in Canada were melting, a large  meltwater lake  formed south of the Hudson Bay.   Geologists have named this  Lake Agassiz , after the  19th century scientist Louis Agassiz. It was dammed to the north by the  Laurentide  ice sheet . Slowly, the ice melted further, and the lake emptied into the sea in a ...

The geological record contains examples of major temperature changes, associated with changes in atmospheric CO2. For example, the   PETM , around 56 million years ago: Matthew Huber at Purdue University calculated that warming slightly in excess of 10 degrees C—like that of the PETM and of pessimistic scenarios for future fossil-fuel burning—could render large portions of the planet uninhabitable for many creatures.  He has said : "There used to be subtropical forests near the poles 50 million years ago, and that doesn’t sound so bad. "But the fossil record closer to the equator is really poor, and that may be an indication that life was extremely stressed during these warm periods. "If over half the surface area of the planet becomes inhospitable, it will not render Earth uninhabitable, but it will be unrecognizable and existentially challenging for the majority of the people, species and communities on Earth." Some researchers suggest  the Palae...

Diagram: NASA Space is not very far away. Aircraft on long-haul flights travel at a height of about 10 km. The lowest layer of the atmosphere, the  Troposphere,  ends at about 15 km. The air in the layers above the troposphere is very thin indeed. Think of a place around 15 km (9 miles) from where you are. That's pretty much how near you are to space. All the waste gases people dump into the air are trapped in the thin layer of air around the Earth. Molecules  in the air include nitrogen and oxygen as well as water, carbon dioxide, ozone, and many other compounds in trace amounts, some created naturally, others the result of human activity. In addition to gases, the atmosphere contains extras such as smoke, dust, acid droplets, and pollen. Atmospheric concentrations   of some   greenhouse gases   over the last 2,000  years.  Stratosphere The stratosphere starts just above the troposphere and extends to 50 kilometres ...

Between about 20,000 and 5,000 years ago, Earth slowly changed from the frigid conditions of an  Ice Age , to the world on which our civilization has developed. As the  ice sheets  melted, colossal volumes of  water  flowed back into the oceans. The  pressures  acting on the Earth's crust changed as a result.  The  weight of ice  on the continents was reduced, and the rising seas put  extra water pressure  on the seafloors. In response, the  crust  moved up and bent, creating extra volcanic activity, increased seismic shocks and giant landslides. So if we continue to allow greenhouse gas emissions to rise unchecked, causing serious warming, will our planet's crust react once again? In Alaska, climate change has pushed temperatures up by more than 3 degrees Celsius in the last half century, and  glaciers  are melting at a staggering rate, some losing up to 1 kilometre in thickness in the last 10...