ESS 221 Documentary 3 – Due 17 May 2017 by 5PM

The Climate Wars: Fightback

The Climate Wars: Fightback presents the last two decades of argument over global warming, particularly looking at what the skeptics of climate change called into question and how science has been used to defend the global climate change argument. Skeptics major arguments include (1) that there is a lack of instrumental temperature data for much of the Earth’s surface, (2) that warming is a natural Earth process, and (3) that warming has nothing to do with carbon dioxide concentrations but is the result of solar activity.

Question 1 (5 Points) – Instrument temperature measurements began around the world in the late 1800s. These records indicate a warming global climate. However, skeptics of climate change point out that thermometer temperature readings leave much of the Earth’s surface without temperature readings. What was used to address this? What did satellite data reveal about the global climate trend? Explain the urban heat island effect and describe how it was used to strengthen the satellite’s data. Was there fault found in satellite data? If so, discuss how this fault supported or rejected the skeptics argument for steady temperatures over the last decades.

Answer: Satellites were used to measure Earth’s temperatures all over the planet, including NASA’s Earth Observatory 2010 (measuring temperature by absorbing microwave radiation). Satellites revealed the Earth’s temperature has remained stable over the past decades; this is contrary to thermometer measures indicating temperatures are rising. Satellite data was further backed by the urban heat island effect. The urban heat island effect says that urban areas are hotter than other areas because (1) roads and concrete surfaces absorb heat during the day and release it at night and (2) tall buildings trap heat within urban areas. Because many of the thermometer measurements were taken from urban areas, this effect is argued by skeptics to have created the false impression of a warming environment.

Satellite data used to support the idea that temperatures have remained stable over the last decades were proven faulty. The friction of the satellite caused the satellite to slow down and get about one kilometer closer to the Earth’s surface each year. This changes not only the temperatures calculated but also the time of day the temperatures were collected: an area that was recorded at midday years later would be recorded in the evening (a much cooler time of day). Once corrections were made to account for the impact of friction, satellite data showed temperatures to be rising at an ever increasing amount over the past decades, supporting the thermometer data.

Question 2 (5 Points) – With rising temperatures now a fact, skeptics argued that the warming was a natural Earth process meaning there is nothing we can do about it as it will continue. Explain evidence for and the significance of the Medieval Warm Period as it related to this skeptic’s argument. Consider Michael Mann’s use of bristlecone pines – what are climate proxies and give an example used by Michael Mann? Explain the Hockey Stick graph and discuss its significant for global warming and against global warming.

Answer: The Medieval Warm Period was a period of high temperatures at about 1000AD. The settling and success of the Vikings in Greenland is evidence of this noticeably warmer period. Greenland was a green and fertile land to support Viking crops and cattle, contrasting from today’s Greenland covered 80% by ice. During this time, the UK also experienced a warm period as grapes were able to grow in England. This evidence promotes the argument that today’s temperatures are not unusual and thus warming is a natural Earth process.

Climate data has only been recorded using instruments for the past century around the world. Proxies are used to infer climates where instrument data is not available and can supplement instrument data where it is available. Tree rings of bristlecone pines were used to infer past climates; thicker rings indicated warmer years. Coral reefs and snow layers were also be used.

The Hockey Stick was the name given to the graph that Michael Mann generated; the graph depicted temperatures over the last 1000 years. The graph showed steady temperatures throughout the past 100 years (with small variations) up until the 1950 where a huge spike in temperatures occurs. Skeptics argue the Hockey Stick to be incorrect because it does not show evidence for the Medieval Warm Period. However, reconstructions by dozens of other scientists reveal that yes, there is high variance within any year’s temperatures; but there is no evidence in the past 1000 years that is as warm as the second half of the 20th century. This promotes the idea that recent rises in temperatures really is unusual.

Question 3 (5 Points) –Skeptics final argument against global warming is that the warming is due to the sun and has nothing to do with carbon dioxide concentrations. Since the Earth’s climate is so dependent on the sun, small changes in solar activity are argued by skeptics to have a big impact on climate. Explain the phenomena of solar sun spots and how they might relate to Earth’s temperatures. Discuss the Little Ice Age as related to sun spots. Discuss the solar activity of the past few decades as it coincides with temperatures and ultimately impacts the skeptic’s argument.

Answer: Sun spots cause waves of charged particles to radiate from the sun causing solar winds. Solar winds blow cosmic rays away; this attributes to fewer clouds on Earth meaning temperatures are higher on Earth. Thus, years of increased solar activity are correlated to warmer Earth temperatures. In the 17th century, there were no recorded sunspots for a 50 year period. This same 50 year period coincides with a particularly cold part of history: frost fails were common, the River Thames froze over, and bitter winters and famine were pervasive. This evidence supports the idea that solar activity and temperature seem to coincide. Thus, the sun may play a significant role in the past. However, solar activity of the past few decades has leveled off while temperatures have continued to rise. Therefore, the sun cannot explain the current temperature highs.