Climate is the average weather conditions present in a particular area over a long period of time. Earth's climate is a complex system essential to our livelihoods. For this reason, scientists, such as paleoclimatologists, hope to better understand future climate conditions by studying Earth's past and present climate conditions. Scientists who study past and present climate conditions have two types of data. The first concerns instrumental data, that 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 disadvantage of instrumental data is that data is only available for the last 150 years or so. In order to study climatic conditions before instrumental data are available, scientists must use indirect data. Proxy data are data collected from natural recorders of climate variability. Some examples of natural recorders are ice cores, tree rings, corrals, and ocean and lake sediments. For example, scientists drill deep into the ice in places such as Antarctica and extract ice cores that may contain air bubbles, dust, and/or oxygen isotopes. These components can then be tested to determine the climatic conditions at the time they were frozen into ice. According to instrumental data over the past 150 years, the Earth's average temperature has increased by 0.5⁰C. As you can see in Figure 1 below, during the second half of the 1800s, Earth's temperature fluctuated from -0.5⁰C to -0.3⁰C. Around 1910, the average temperature began to increase steadily until the 1940s, reaching temperatures almost above average. Starting in the early 1980s, a...... middle of paper ......areer, such as the Arthur Fleming Award in 2006 and the NOAA Administrator's Award for Excellence in Scientific Research in 2003. He has published or co-published several peer-reviewed works and participated in several field exercises. In other words, Dr. Anderson is a qualified person to present information about the Earth's climate. Works cited by Anderson, Dr. David, Dr. Carrie Morrill, and Dr. Eugene Wahl. A paleo perspective on global warming. NOAA. July 2009. The web. February 2012. http://www.ncdc.noaa.gov/paleo/globalwarming/home.html “Ice cores and climate change”. British Antarctic Survey.2007. Internet. February 2012. http://www.antarctica.ac.uk/bas_research/science_briefings/icecorebriefing.phpJones, Phil. World temperature record. Climate Research Unit. January 2012. The web. February 2012. http://www.cru.uea.ac.uk/cru/info/warming/