ROCKY REX'S SCIENCE BITES

What is the worst-case scenario for climate change? The geological record shows that when the atmosphere suddenly changes, there are big effects on living things. Five major   mass extinction   events are recorded in the rock record of the last 600 million years. The biggest extinction was at the end of the   Permian ,  around 252 million years ago. It is called the   End-Permian mass extinction. Only about 8% of species survived to live on in the Triassic Period. Chongqing Special Administrative Region (SAR) in central China, showing a hillside that includes rocks crossing the end-Permian extinction event and the Permian-Triassic boundary. Researchers have found evidence of a compound called fly ash, one of the products of coal combustion, in rocks laid down just before this extinction event.  A large amount of coal had been burned over a period of tens of thousands of years. The  coal was burned by volcanic eru...

W hy can’t recent  climate change  just be an effect of 'natural causes'? There have been climate changes in the past 2000 years. People talk about times called the  Medieval Warm Period  and  the  Little Ice Age . Careful research  has shown that the current temperature is warmer than the Medieval Warm Period - temperatures between 1000 and 1100 AD were probably similar to parts of the 20th century, but 21st century temperatures are already warmer. The Medieval Warm Period may not even have been a global event -  glaciers on Baffin Island   were no smaller during that time. A particularly cool period is often called the   Little Ice Age. However,   the name "Little Ice Age" is now regarded by some scientistsas misleading. The best estimate of the drop in temperature is, at most, 0.5°C,  compared to the temperature decreases in "real" ice ages of about 8°C.   Also, the "Little Ice Age" only lasted for 500 years ...

Some people confuse 'climate' with 'weather' - but i f 'climate' and 'weather' are the same, why would there be two words? Other people say "We call climate change 'winter' and 'summer'...."   What does the word ' climate ' mean? It normally means  the average of conditions over 30 years . Climate  normally means 'an average over 3 conventional decades'. A  conventional decade  is, for example, 2001-2010, or 1961-1970. So ..... 3 full, conventional decades......such as 1981 to 2010. For example .... rainfall in Ireland. And another example -  ' A verage temperature 1951-1980' The definition of 'climate' goes back at least 100 years. So if we are discussing  climate change , that is what 'climate' means. But in recent times, there has been a lot of variation in global temperatures. So it can be useful to look at  single conventional decades . ...

Carbon dioxide  levels in the atmosphere are rising. This graph showing the data is called the  Keeling Curve . The small up-and-down pattern is caused by changes during each year -  in the summer in the northern hemisphere, there is more photosynthesis which causes CO2 levels to fall. The Keeling Curve is named after the scientist who first produced accurate measurements of carbon dioxide in the air -  Charles David Keeling.     Charles David Keeling in the lab. Keeling's collection of data began in 1958. Concentration is measured in  p arts  p er  m illion (ppm) March 2015 was the first time for hundreds of thousands of years that CO2 exceeded 400 ppm for a whole month. Ice core data  shows humans have never breathed air containing so much CO2. Since Keeling began recording, CO2 has risen from 318 ppm to 400 ppm... a rise of around 25%.   The fastest rise of CO 2  in the air seen in   the ice...

According to the  Royal Society ....... If human emissions of CO 2  stopped altogether... .... it would take thousands of years for atmospheric CO 2  to return to ‘pre-industrial’ levels. " The climatic impacts of releasing fossil fuel CO 2  to the atmosphere will last longer than Stonehenge, " says  University of Chicago oceanographer  David  Archer. "Longer than time capsules, longer than nuclear waste, far longer than the age of human civilization so far." Why is that? It takes a long time for deep oceans to bury the carbon dioxide in ocean sediments.  Lifee on the abyssal sea floor (depths ranging from 4000-6000 m) near the Hudson Canyon off the coast of New Jersey. Photo taken using the Deep Submersible Research Vessel (DSRV)  Alvin's camera system.  Image courtesy of Deep East 2001, NOAA/OER. Surface temperatures would stay high for at least a thousand years. Humans would face  a warmer planet due to past and curre...

The  Arctic   includes an  ocean covered by sea ice. Arctic sea ice  melts back in Summer, and then refreezes in Winter. The  area  of Arctic sea ice is largest in March each year, and at its lowest each September. It is reducing over time  - the graphs come from the US  National Snow and Ice Data Center. The NSIDC also publish this graph, which is normally updated every day. More graphs and other data are also available from the  Arctic Data Archive System , operated by the Japanese  Arctic Environmental Observation Center. The total volume of Arctic sea ice has declined dramatically over time. New research   shows the decline in Arctic sea ice area since 1850: Research suggests   the remarkable decline of   Arctic sea ice over  the last century is far beyond anything seen for a long time.  

The  permafrost  of places like  Siberia  is not so permanently frozen any more. As it slowly melts, wonderful things are emerging, some frozen for tens of thousands of years. Baby mammoths  are sometimes found in an extraordinary state of preservation. "As the Earth warms, scientists worry that some of the carbon in permafrost could escape to the atmosphere as carbon dioxide or methane.  Increasing the amount of these gases in the atmosphere could make Earth's climate warm up even more." Arctic permafrost – ground that has been frozen for many thousands of years – is now thawing because of global climate change.  There are many effects of global warming, including melting permafrost, discussed in this useful document:  Physical effects of warming. The results of melting permafrost could be  disastrous and irreversible.

Scientists have   observed an increase in carbon dioxide’s greenhouse effect   at the Earth’s surface.    The graphs show carbon dioxide’s increasing greenhouse effect at two locations.  The first graph shows CO 2  radiative forcing measurements obtained in  Oklahoma .  The second graph shows similar upward trends in  Alaska . (Credit: Berkeley Lab) The researchers link this to rising CO 2  levels from fossil fuel emissions. Radiative forcing  measures how the planet’s energy balance is altered by atmospheric changes.  Positive radiative forcing  occurs when the Earth absorbs more energy from solar radiation than it emits as heat radiation back to space. “We see, for the first time in the field, the amplification of the greenhouse effect because there’s more CO 2  in the atmosphere to absorb what the Earth emits in response to incoming solar radiation,” says Daniel Feldman. Dr Feldman is a  sc...

Burning  fossil fuels  produces  carbon dioxide . Carbon dioxide emissions  need to be limited.   However, the potential carbon dioxide emissions contained in fossil fuel reserves are vast. So   it's not possible for all current fossil fuel reserves to be used,  if the Earth's warming is to be kept below 2 °C.  This huge excess quantity of fossil fuel is sometimes called the  'Carbon Bubble'. However, there are   major objections  even to the "two-degree limit" . Many say the number is simply too high. Archbishop Desmond Tutu has  pointed out   that a two-degree global average rise might result in Africa’s temperature rising as much as 3.5 degrees—a potentially disastrous change. Various scientific research projects have looked at what would happen if all the fossil fuels were burned. One project concluded: The Antarctic Ice Sheet stores water equivalent to 58 metres in global sea-level rise....

The chaotic nature of  weather  makes it unpredictable beyond a few days.  To predict the weather you need to know exactly what is happening in the atmosphere down to the smallest scale.  Climate  is the  average weather pattern  of a region over many years (usually a period of 30 years). Weather forecasts  depend on knowing exactly what is going on in the atmosphere, down to the smallest scales.  Climate forecasts  look for patterns over a longer time.  Will it be generally wetter in winter?   Will there be more heavy downpours? A paper  published in the journal  Science  in August 1981  made several projections regarding future climate change. The projections were rather accurate — and their future is now our present. "Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climate zones,...

Summer in the south, winter in the north. 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.

"Climate sensitivity" is the term used for the amount of global warming to be expected if we double the amount of CO2 in the air. For thousands of years CO2 concentration was around 260 ppm to around 280 ppm - s ince the Industrial Revolution it has risen to over 400 ppm. The graph of CO2 concentration as recorded since the 1950s is known as the Keeling Curve, named after Professor   Charles David Keeling , who began the regular measurements of this value. If we get to around 560 ppm CO2 (around twice the pre-industrial level) we might well get to more than a 3 C degree rise, as that's a plausible value of climate sensitivity as reported by research from the geological record. Climate sensitivity is well-researched from the geological record in this paper: "Making sense of palaeoclimate sensitivity" - Rohling et al, 2012. a warming of 2.2–4.8 K per doubling of atmospheric CO2 Even the lower value would have serious consequences, and the p...

Farmers can put up with some bad weather, but  climate change  will make unusual events more likely. 20-30% of plant and animal species will be more likely to become extinct if the temperature rises by more than 1.5-2.5C. There will be big effects on farming from droughts and floods. The biggest effects will be seen first near the  Equator . Just  being near the Equator  makes it more difficult for countries to make economic progress. Hotter conditions affect how crops grow. Our agriculture is heavily reliant on  grasses  from the temperate regions. Corn, wheat, and rice  are all types of grass. The Tropics will expand as the world warms, so the world will find it harder to grow those important crops. People will  try to leave places  where they cannot produce enough food. Countries where  food prices  rise rapidly tend to become unstable, making  conflicts  more likely. Global w...