Climate Change Indicators and Evidence

Temperature Changes Temperature records can be gathered from around the globe and have been consistently monitored in locations for many decades for accuracy and reliability of data. According to NASA, 2014 was the warmest year on record

Long Term Temperature Changes Question: How do we know what the temperature was thousands of years ago? Answer: ice cores, rock, tree rings, ocean sediments, coral reefs and landforms can give clues to past climate!

Ice Cores An ice core is a core sample from the accumulation of snow over many years that have recrystallized, forming ice sheets, and have trapped air bubbles from previous time periods. Provide the longest record of conditions in the atmosphere Drill deep into the ice and then cut out small sections to analyze the air pockets. Analysis can give information about: – Amount and type of GHG present – Air temperature – Precipitation levels – Volcanic activity

Ice Accumulation Generally, more ice (sea ice and ice sheets) means that the climate is cooling. Ice will accumulate when summer temperatures are not warm enough to melt away the previous season’s ice. Extra accumulation may impact summer temperatures by reflecting more sunlight (albedo effect). So the winter does not need to be especially cold providing that the summer is cool enough to allow the ice to survive into the next winter.

Changes in Arctic Ice Ice cover in Arctic depends in part on ice which survives the summer melt each year. In 2009, ice older than two years accounted for <10% of ice cover (between , figure was ~30%) Younger ice is thinner and more prone to melting during summer months

Ocean Salinity Thermal energy transferred around the world’s oceans via the Great Ocean Conveyor Belt, which is powered by differences in water temperature (& density) and salinity Global warming causes ↑ in freshwater into ocean via glacier melting, precipitation and run-off. Dilution of ocean’s salinity would make ocean water less dense = slowing down the belt!

Sea Level Changes The ↑ in ocean temperatures will not only melt polar ice & glaciers. It will also make the volume of water in oceans expand. – If the sea surface temperature ↑ by 1.4°C, sea levels will rise ~15 cm! – Warmer water = more intense weather and less aquatic species (therefore, CO 2 sink activity ↓ and more CO 2 goes into atmosphere) As waters rise, there is a greater risk of edges of ice shelves and coastal glaciers collapsing into the sea, thereby causing further sea level rises. Low lying countries and island nations as well as coastal cities will be affected!

Coral Bleaching Many sea organisms rely on coral reefs as a habitat Corals have a mutualistic relationship with photosynthetic algae called zooxanthellae. Corals get O 2 from them and algae get a habitat. ↑ in ocean temperature affects the zooxanthellae. Without the zooxanthellae, the corals turn white (bleaching process). Bleached coral are weak and less likely to survive. Additionally, ↑ in CO 2 levels means that the oceans absorb more of it, which makes the oceans become more acidic. This makes the corals less likely to absorb the calcium carbonate in the ocean that they need to maintain their skeletons. Healthy Unhealthy (acidic)