GLOBAL WARMING: A Team Debate.

== Framework == For something to be a threat, there only needs to be a reasonable probability that it can cause harm in the future. In contrast, to show that a threat to the environment does not exist, our opponent’s must prove beyond a reasonable doubt that there is no possibility that human-caused climate change can cause harm in the future. Our opponent’s burden comes, in part, from the precautionary principle, which holds that we should not take any actions that fundamentally alter our ecosystem (such as emitting large amounts of CO2) unless we are absolutely certain that there will not be problematic consequences to doing so in the long-term. The justification for the precautionary principle is that environmental harm is irreversible and the long-term effects are hard to predict, so we should be extremely certain that our actions will not cause harm before fundamentally altering our ecosystem. == Case == Contention 1: Human-caused global warming exists The International Panel on Climate Change (IPCC) is an international group of some of the world’s most respected scientists. The IPCC has published five different reports on climate change. With each subsequent generation of report, the reports get more accurate because more datasets become available. First, warming is happening now. According to the IPCC’s fifth report on climate change: "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and oceans have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased." [IPCC 5, http://www.ipcc.ch...] "It is virtually certain that globally the troposphere has warmed since the mid-20th century." [IPCC 5] The IPCC defines "virtually certain" as having a 99-100% confidence level. [IPCC 5] The IPCC also says it is virtually certain that we will have more hots days and fewer cold days over major land areas in the future. [IPCC 5] The IPCC says that it is virtually certain that increased cyclone activity is caused by global warming. [IPCC 5] "It is virtually certain that the upper ocean (0-700 m) warmed from 1971 to 2010." [IPCC 5] The IPCC says that it is virtually certain that permafrost levels will continue to decline due to global warming. [IPCC 5] "It is virtually certain that global mean sea level rise will continue beyond 2100" due to global warming. [IPCC 5] The IPCC report also contains numerous findings that are "very likely" (90-100% confidence level), but for the sake of saving space, we won't excerpt them here. Second, recent warming is caused by human activity. "The evidence for human influence has grown since [the previous IPCC report]. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century." [IPCC 5] "Extremely likely" is a 95-100% confidence interval. [IPCC 5] Today’s atmospheric CO2 levels are 40 percent higher than the highest natural level of CO2 that has ever existed in the last 800,000 years. [EDF, http://www.edf.org...] We know that most of the increase in CO2 levels is due to burning coal and gasoline because the composition of the CO2 has a unique fingerprint that allows scientists to determine its source. [EDF] Another human activity that has increased CO2 levels is the massive clear cutting of the rainforests, which formerly acted as a huge carbon sink, absorbing large amounts of CO2. [EDF] Deforestation adds 1,500,000,000,000,000 grams of carbon to the atmosphere each year. [GCP, http://www.globalcarbonproject.org...] Thus, humans contribute greatly to global warming. The data proving that human-caused global warming exists has become so overwhelming that it has converted former climate skeptics, such as University of California, Berkeley, professor Richard Muller. Muller writes: “"Call me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause. [New data from UC Berkeley] show[s] that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases. [The UC Berkeley data set is] stronger than those of [previous IPCC reports]." [NYT, http://www.nytimes.com...] Third, there is significant evidence in the paleoclimatic record that greenhouse gasses have a significant effect on the global temperature. Over the Cenozoic Era, which began about 66 million years ago, we can see a clear greenhouse induced warming effect within the various warming and cooling cycles. It remains very clear that CO2 remains the main driver of climate in this period. The large climate changes over the period cannot result from shifts in the climate system, but depend on both energy coming into the planet (e.g. solar rays) and changes in the atmosphere (greenhouse gasses). The sun, however, cannot be considered the dominant force of climate change in this time period because the luminosity increased by about 0.4% over this period. That alone cannot explain the warming during the Cenozoic because the Cenozoic has also seen a period of decreasing temperatures, which could only be explained by fluctuating CO2 levels (from 1000 ppm at the beginning of the Cenozoic to a low of 170 ppm). If the sun was responsible for the warming during this period, we’d see only a constant increase in temperatures. Continental movement also is unlikely as an explanation for the observed climate change during this period due to the fact that “most continents were near their present latitudes at the beginning of the Cenozoic.” Studies have concluded that “CO2 was the dominant climate forcing in the Cenozoic” [Hansen & Sato, http://www.columbia.edu...] Contention 2: Future harm from global warming By 2100, global warming is estimated to cause $1.9 trillion per year in economic damages to the United States. [NRDC, http://www.nrdc.org...] The damage includes $360 billion from destroyed real estate due to rising sea levels, $141 billion in higher energy costs due to higher demand for air conditioning, $950 billion due to the cost of providing water to places where it dries up, and $422 billion in damages from the increase in tropical storms due to global warming. [NRDC] Future sea level rise, even by conservative estimates, are significant and would threaten “some coastal cities and low-lying island nations.” The low estimates--assuming less than 2 degrees celsius warming and a decreased temperature trend after 1950--find that there will be about half a meter sea level rise by the year 2100. [Horton et al., http://www.sciencedirect.com...] Food production, important to the well being of society, also represents a large industry: about $200 billion a year to the US economy. Agriculture is dependent upon certain climatic conditions and altering these could prove to be catastrophic. While an initial increase in temperature may help some crops, once temperatures pass the crop’s optimal levels for growth and reproduction, increased warming becomes counterproductive. [EPA, http://www.epa.gov...] Some crops, like grains, grow faster when the climate is warmer, but because these crops grow faster, they have less time to fully mature, so they produce fewer edible byproducts. [EPA] Further, weeds thrive in warmer climates with more CO2 enrichments. Farmers already spend $11 billion a year combating weeds. Future temperature increases would add another burden to the industry [EPA]. Lastly, climate change dries out and acidifies soil, further impacting food production. [IPCC 4, https://www.ipcc-wg2.gov...] Many theoretical models exist claiming that certain diseases would become more common as the climate changes. For example, increased temperatures will allow the virus that causes dengue fever to survive in more places. In 1990, 30% of the world’s population lived in regions where the estimated risk of dengue fever transmission was 50%. By 2085, 5-6 billion people (about half of the future estimated population) would live in areas where they were at risk of dengue transmission. If climate changes do not occur, only 35% of the population would be at risk. [Hales et al., http://www.ncbi.nlm.nih.gov...] Conclusion As you can see from our prior contentions, man made global warming is in fact a threat and can cause a great deal of harm. Even if Con casts some doubt on the harm caused by global warming, as long as we win that some harm is probable, we win this debate. Almost any amount of harm is enough for you as the judge to affirm the resolution that global warming is a threat. For the Con team to win this debate they must negate all of our contentions and statistics along with building a case of their own showing that there is in fact no threat from global warming. We can clearly see from the prior contentions that there is indeed a threat and it can and will cause harm.