Climate is the average weather conditions present in a particular area over a long period of time. Earth’s climate is an intricate system that is essential to our livelihoods. It is for this reason that scientists, such as paleoclimatologist, are hoping to better understand future climate conditions by studying the Earth’s past and present climate conditions.
There are two types of data available to scientist studying past and present climate conditions. The first is instrumental data, which is observed data that can be measured by weather monitoring instruments. Some examples of weather monitoring instruments are thermometers, rain gauges, weather balloons and satellites. The downside to instrumental data is that data is only available for the last 150 years or so. In order to study climate conditions before instrumental data was available, scientists have to use proxy data. Proxy data is data collected from natural recorders of climate variability. Some examples of natural recorders are ice cores, tree rings, corral and ocean and lake sediments. For example, scientist drill deep into ice located in such places as Antarctica and extract ice cores that can contain air bubbles, dust and/or isotopes of oxygen. These components then can be tested to determine the climate conditions at the time the components became frozen in the ice.
According to instrumental data from the last 150 years, the Earth’s average temperature has risen by 0.5⁰C. As you can see in Figure 1 below, during the later half of the 1800’s Earth’s temperature fluctuated from as low as -0.5⁰C to as high as -0.3⁰C. Around 1910, the average temperature began a steady incline until the 1940’s to almost above average temperatures. Beginning in the early 80’s, after 30 years of below average temperatures, the Earth’s temperature began another steady increase to 0.4⁰C above the average base temperature (dataset from 1960-1990).
Figure 1: Global Temperature Record – Phil Jones
(Credit: Climatic Research Unit, http://www.cru.uea.ac.uk/cru/info/warming/)
Proxy data has shown in the last 2,000 years, the Earth’s average temperature has been pretty consistent with a few small rises and falls from about 200AD until about 900AD. Figure 2 below, shows that around 900AD, the Earth experienced a small warming period. This warming period, referred to by scientist as the “Medieval Warm Period”, lasted for about 200 years. After another 200 years of pretty consistent temperatures, the Earth experienced what scientist call the “Little Ice Age” from about 1400AD to about 1800AD. As we can see from the instrumental data above, proxy data also confirms a steep incline of the Earth’s temperature in the first half of the 20th century and continuing on into the 21st century. Such accelerated temperature increase is something the Earth had not experienced in the first millennium AD; possibly ever.
Highly variable Northern Hemisphere temperatures reconstructed from low- and...