ROCKY REX'S SCIENCE BITES

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...

Climate change is getting worse but it is no worse than we predicted 4 May 2020 Members of the Committee on Climate Change The witness accounts of bush fires and floods only add to people’s awareness of the worsening climate crisis. However, these types of impacts are generally neither worse, nor happening faster, than we thought. An increase in extreme events on the scale observed was foreseen by successive scientific assessments from the Intergovernmental Panel on Climate Change (IPCC). Worsening climate change should not be mistaken for individual events that are worse than expected. Recent extremes give a clear picture of the impacts and risks that come with a human-driven warming climate. Extreme events also emphasise the urgency of action to achieve Net Zero greenhouse gas emissions and adapt to climate change, write  Professor Piers Forster and Professor Corinne Le Quéré. We are increasingly witnessing and learning more about the costs of climate change fo...

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...

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  swept through many areas, destroying homes and wildlife. It is estimated that around a billion animals died. 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...

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, and floods the delta-top. 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.

Professor Hannah Cloke ,  from the University of Reading   " .... for every decade I have been on this planet, it has been getting hotter and hotter and hotter." The EU's Copernicus Climate Service reports that 11 of the 12 warmest years on record on the continent have occurred since 2000. "Europe has indeed been warming significantly faster than the global average," said  Professor Rowan Sutton , director of science (climate) at the UK's National Centre for Atmospheric Science. The full report https://climate.copernicus.eu/ESOTC/2019

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...

View of the Heel Stone at summer solstice sunrise, as seen from inside the  Stonehenge   monument. Image via   mysticrealms.org A  solstice  happens when the Sun in the sky is at its furthest point from the celestial equator.  In 2020 the Summer Solstice in the northern hemisphere happens on the 20th June.   At the June solstice, the Sun reaches its northernmost point, as the Earth’s North Pole tilts towards the Sun, at about 23.5 degrees.  Apart from the well-known links between the solstice and  ancient stone structures , another extraordinary ancient object has connections to this celestial phenomenon. The  Nebra Sky Disc  is a 3,600-year-old bronze disc which, according to UNESCO, features the oldest known depiction of cosmic phenomena in the world. The disc is such an extraordinary piece that it was initially believed to be a forgery. The  Nebra Sky Disc  was discovered in 1999 by two amateur trea...

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 ...