ROCKY REX'S SCIENCE BITES

Marlin  can hunt in water a half mile down, and sailfish often dive deep too. In more and more places around the world, ocean predators are sticking near the surface. Why? Warming temperatures are  sucking oxygen out of waters  even far out at sea, making enormous stretches of deep ocean hostile to marine life. New research  shows that this problem is getting worse. Vast stretches of the ocean interior  suddenly lost oxygen  during the transition out of the last  glacial stage , between 17,000 and 10,000 years ago.  This event was the most recent example of large-scale global warming. There are other examples in the geological record, including the  Zechstein Sea.

This graph shows how  carbon dioxide  has increased and decreased over hundreds of thousands of years. The low readings match with times called ' glacial stages '. During glacial stages,  ice  covered large areas of the Earth. The peaks in the graph show times when carbon dioxide was high, matching times called ' interglacial stages '. The most recent glacial stage occurred between about 115,000 and 11,500 years ago.   The  last interglacial period  occurred before it, from around 130,000 to 115,000 years ago. It's official international name is the  Eemian,  but it has other names in specific places. Climate information from that time is particularly useful. During that time,  temperatures  on earth were higher at the poles than they are now.  The  sea level  was between five and nine metres higher than current levels, because of the melting of ice in  Greenland  and  A...

The climate can react to sudden shocks. The weather in  1816  was very strange.  Spring arrived, but then everything seemed to turn backward, as cold temperatures returned.  The sky seemed permanently overcast.  T he lack of sunlight became so  severe that farmers lost their crops. Food shortages were reported in Ireland, France, England, and the United States. 1816 became known as  "The Year without a Summer"  or "18-hundred-and-frozen-to-death". It was over 100 years before anyone understood the reason for this weather disaster. The eruption of an enormous volcano on a remote island in the Indian Ocean a year earlier had  thrown enormous amounts of volcanic ash  into the upper atmosphere. The dust from  Mount Tambora , which had erupted in early April 1815, had shrouded the globe.  With sunlight blocked, 1816 did not have a normal summer. In Switzer...

T he  Gulf Stream  transports vast amounts of heat north, from the equator to the pole, passing off the East Coast of the U.S. and into the North Atlantic. The  Northern Hemisphere winter of 2014-15  was the warmest on record globally, according to the National Oceanic and Atmospheric Administration.  But one area of the  North Atlantic   was the coldest on record... shown in blue on this map. This cold pool may be  an indicator of a dramatic slowdown in the  Gulf Stream. A slowdown like this in the current has not happened for a very long time, perhaps as long as 1,000 years.  It is possibly related to the melting of the  Greenland  ice sheet.  The  freshwater  from the ice sheet  is  lighter  than heavier, salty water that usually occupies that area.  It tends to sit on top of the water,  interfering with the sinking of dense, cold and salt-rich water. The Gulf Stream transpo...

Oil is a  fossil fuel . It was formed from chemicals from ancient living things. To make the chemicals in oil, the  temperatures  and  pressures  needed to be just right. The oil (and gas) will only stay in the reservoir if there are  suitable structures  in the rocks: The carbon compounds from the plants and animals have been trapped for hundreds of millions of years. They have been burned to make carbon dioxide in a very short time. The amount of carbon dioxide in the air has changed very quickly. Diagram of how oil is made Source:  Library and Archives Canada © Library and Archives Canada

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 ...