You know those statements you hear that make you go ‘oh, well that sounds plausible’. Yup, they’re often a complete load of twaffle. Here’s some of the usual suspects, except we’ve armed you with the real facts. Whenever you hear stuff like this, never be afraid to ask for the facts they’ve based their opinions on (usually some opinionated radio jock, lunched-up by the oil companies). It’s all about balance. Too much CO2 for Earth to process. Argument 1. “The climate has changed before throughout history – this is just part of the natural cycle and doesn’t have anything to do with humans”. The Science: There have been several times that the Earth’s climate has warmed, each time due to increases in greenhouse gas emissions and each time proved highly destructive for life, caused mass extinctions, ocean acidification and rising sea levels. So we KNOW that changes in greenhouse gases have a direct relationship on changes to the Earth’s climate. An increase in the gases, primarily CO2 (carbon dioxide) and CH4 (methane) heat the Earth, while a reduction in the gases sees the temperature drop. Before the onset of anthropogenic (caused by humans) emissions, these increases came from natural sources, such as massive volcanic activity on our young planet, but we don’t experience that now. In the Eocene and Cretaceous periods there were high levels of CO2, but life flourished as the amounts of greenhouse gases were in balance with the carbon in the oceans. However, over the past 200 years, humans have emmitted massive amounts of CO2 at a rate faster than can be balanced out. The climate does change naturally due to the Milankovich cycles, which determine the angle of the Earth as it travels around the sun and has produced warm (interglacial) and cold (glacial) periods. But these are cycles are not related to greenhouse gases and we can relate them to the the planet’s transitional path. Therefore: The current climate change is due to human activity by producing more greenhouse gases than our planet can handle. Argument 2. “Periods in the past have been warmer than today – this shows the climate warmed even before humans started emitting greenhouse gases” The Science: People here are probably referring to the Medieval Warm Period (950-1250AD). There is no debate that it occurred, but the causes for it are contested. It is generally agreed that the Warm Period was the result of a number of climate systems, including: • changes in ice albedo (reflectiveness) • changes in vegetation • seasonal shifts • a Dansgaard-Oeschger event (warming possibly due to changes in Atlantic ocean circulation) • interaction between the NAO (North Atlantic Oscillation) and the La Nina phase of ENSO • increase in solar radiation • lack of ‘cooling’ volcanic eruptions (produces methane, but particles blot out sun) Temperature reconstructions of the Medieval Warm Period show that average SST (sea surface temperatures) were within 1°C of current temperatures, but the latest IPCC report predicts a massive increase of sea temperatures, up to 6.4°C by 2100. Yikes! In 2009, an answer was found in the annual growth rings of Moroccan atlas cedar trees and the stalagmites that grow in a Scottish cave beneath a peat bog. What they showed is just how wet it had been in these regions during the Medieveal Warm Period. Morocco is affected by a strong high pressure system called the ‘Azores High’ whilst Scotland is affected by a low pressure system called the ‘Icelandic Low’. The pressure difference between the two meant there was a very strong positive North Atlantic Oscillation (NAO). This is an ocean current that drives warm winds from the Atlantic over Europe….so it got pretty warm at that time! Now, there’s a bit more to this research, but it involves even more acronyms…and you’ve probably suffered enough. But what they did work out, was that Medieval Warm period was regionalised, meaning that it warmed in some areas, instead of producing a general world-wide warming. Therefore: There was a previous period of warming, but we can prove what caused it, and it wasn’t humans. We can also prove that climate science is very complex and involves more anacronyms than is sensible! Argument 3. “The sun is causing global warming” The Science: This argument goes along the lines that there are an increasing number of sunspots, which coincide with periods of high solar activity and therefore the spots must contribute to warming the planet – just like in the apocalyptic film ‘2012′. This is a direct example of correlation does not equal causation. The sun is our dominant source of atmospheric heat, but has actually cooled slightly recently. This is occurring whilst global temperatures are increasing, so it doesn’t make sense to anyone that the sun could be causing global warming. Climate deniers have cherry picked the data where increases in sun spots and temperature correlate, and ignore other periods where they don’t match up. Earth getting warmer – Sun getting cooler. Therefore: No, the sun is definitely not causing global warming as the sun is actually cooking slightly.…awkward. Argument 4. “Scientists don’t agree on climate change” This argument is one circulated by the mass media and often sponsored by organisations who benefit by perpetuating the argument. The ‘Petition Project’ is an example of this. It was set-up by a small group of scientists who aim for ‘health and longevity’ (reducing food intake cures cancer etc). They claim to have 31 000 signatures of American scientists who don’t support the idea of human-caused climate change. Now at first, this might sound startling, but they’re pretty liberal with who they include as ‘scientists’. In fact most are engineers, they also include food and computer scientists, who lets face it, don’t exactly have a curriculum full of climate studies. The only scientists with enough knowledge on the matter to make a legitimate statement of fact, are climate scientists…of which they had just 39, and of course, it’s impossible to check and validate these entries. However, even if we did believe that the 31,000 were scientists with climate knowledge, compared to the number of those with graduate degrees in these areas, this means that only a minute ~0.3% of scientists in the US don’t believe climate change is caused by human industry. Awkward! In reality, 97% of published climate science research papers agree that climate change is real and primarily caused by humans, specifically the burning of fossil fuels. Remember that there are scientists producing papers on climate change who are sponsored by climate-denier organisations. These papers come under great scrutiny of peer review, meaning that it has been determined as legitimate by many qualified and independant scientists. Therefore: 97% of scientists agree that climate change is produced by man. The 3% are possibly employed by climate-denier organisations and need to adhere to those sentiments, or have not read the research papers on climate change. Check out http://theconsensusproject.com/ for more information on how climate scientists agree on climate change and this hilarious segment on Last Week Tonight: Argument 5. “The climate is cooling, not warming” The Earth switches between cold (glacial) and warm (interglacial) periods. Currently, we’re about 18,000 years into an interglacial period and heading towards the next cold snap. However, we’ve a while to wait as this change to cooler climate will be occurring in thousands of years, but the focus on climate change looks at the present and into the next hundred years. Thorough examinations of the Earth’s past and current climate show evidence of global warming; air temperatures (over land and sea) are increasing, snow cover is decreasing, ice is melting, sea levels rising and sea surface temperatures increasing. Sceptics tend to take selected evidence where cold records are being broken in comparison to the recent past, whereas heat records are being set over all time. The evidence is overwhelming. Therefore: The climate is due to cool in thousands of years time…but right now, all evidence proves the Earth is warming. Argument 6. “Climate models are unreliable” Climate models are incredibly complex mathematical representations that consider all interactions between the atmosphere, oceans, surfaces and incoming solar radiation….can you imagine the massive amounts of data that produces! Models use data recorded from the past and present to project trends about the future (not specific events). These models are heavily tested by a process called ‘Hindcasting’, where the models use data from previous times to see if they can accurately predict trends. Models which incorporate additional amounts of CO2 successfully map current trends of warming, whereas those who do not include extra CO2 don’t fit the data readings – this shows that CO2 is a major contributor to climate change. Models have successfully predicted the climate recovery after the Mt. Pinatubo eruption, where large amounts of gas and aerosols (tiny particles in the atmosphere) cooled the climate. They have also correctly predicted warming over the Arctic areas. One of the main arguments against climate models is that they take the worst-case scenario and over-exaggerate things, but so far actual data is proving closer to the ‘worst case scenarios’ than milder predictions. Models are constantly being improved with new satellite data and climate scientists constantly investigate ‘uncertainties’ in their models, but so far they’re doing a pretty good job. For example, this is a model based on sea level rise – it’s clear to see just how well the predictions of the model fit with data from the tide gauge. It’s more than a bit scary that the actual observations fit the upper ‘worst case scenario’ of IPCC (Intergovernmental Panel on Climate Change) projections. Therefore: Climate models are proving accurate…and getting better. Argument 7. “The ‘hockey stick’ is wrong” Not so Jolly Hockey Sticks! The ‘hockey stick’ refers to the sharp incline in global temperature recordings in the past 100 years in comparison the previous 1000 years – the shape looks a bit like a hockey stick (well it does to climate scientists!). These readings were based off ‘proxies’ (ie, not direct climate data like atmospheric samples) such as corals, stalagmites, tree rings, boreholes and ice cores. Climate sceptics determine the trend as nonsense and full of errors, where in actual fact the data from the proxies proved that the climate cooled over the past 1000 years and took a sharp upturn in the 20th century as temperatures continually broke heat records. Studies confirm the original hockey stick model; that the climate dramatically warmed after 1920 (when the effects of the Industrial Revolution kicked in). Downwards slant, then sharp upturn = the hockey stick Therefore: The ‘Hockey Stick’ model is jolly hockeysticks correct – the climate suddenly got hotter Argument 8. “It’s been really cold – so much for global warming” There is a difference between weather and climate. Weather refers to atmospheric conditions over a short period of time, whereas climate looks at trends which develop over many years. Long-term trends over the past 100 years show that the climate is warming significantly. Temperature fluctuates all the time on a seasonal basis and especially with the effects of the ENSO (El Nino Southern Oscillation). Climate scientists read the long-term trends from temperature graphs and do not take into account short-term temperature fluctuations. It’s easy to manipulate temperature readings to present data to show the climate cooling by pulling out data ofs hort durations – climate sceptics generally cherry-pick data to portray the climate as cooling in this respect. However, the fantastic thing about science is that you can’t argue with facts. NASA data shows since 1998, the temperature has been the hottest in all recorded temperature history, and that a strong and significant warming trend is evident over all data records. Definitive global temperature rise Therefore: Global temperatures are steadily warming, but there are still seasonal and local variations. Argument 9. “Human emissions are insignificant compared to natural emissions” The Earth functions with a natural carbon cycle that transports carbon around the environment between the land, sea and atmosphere in sources and sinks. This cycle is naturally kept in balance, but humans upset this balance by continually adding CO2 without removing any. A build-up of gas is never good! Looking at gases trapped in air bubbles in ice cores, we know that carbon dioxide levels have remained about 180-300 ppm for the past half a million years. However, in recent centuries as humans started burning fossil fuels, carbon dioxide levels have risen to about 380ppm. The natural carbon cycle emits and absorbs massive amounts of CO2 (about 750 giga-tonnes), in comparison to human emissions which are about 29 gigatonnes. So…what’s the problem? About 40% of extra CO2 emitted is absorbed by the oceans, which are a massive carbon sink. The rest hangs around in the atmosphere and contributes to the greenhouse effect because the carbon cycle can’t process all this extra CO2 – humans are upsetting the carbon cycle. As a result, CO2 levels are now the highest they’ve ever been in 15 -20 million years. Therefore: The amount of CO2 we produce is more than our Earth can absorb. It’s as simple as that. We MUST massively reduce our CO2 emissions. Argument 10. “But…water vapour is the biggest greenhouse gas” Water vapour is technically the most dominant greenhouse gas. There’s an awful lot of water on our planet, when temperatures warm, water evaporates (converts to a gas). You can see some water vapour in the form of clouds. Fluffy white cloud turns eco-killer! You’d have noticed that if there’s a lot of cloud cover at night, it’s not as cold as if it was a clear sky. This is because the clouds act as a sort of blanket to our lower atmosphere, trapping the warm air in. But if you add more CO2 and other greenhouse gases than our Earth can handle, the global warming that is produced, causes more heat, which means more water evaporates into vapour, which means even more heat is trapped in our atmosphere. This is called a positive feedback system. The IPCC doesn’t really classify water vapour as a greenhouse gas because it is part of this system, and not just a forcing agent. But we do know that any increase in temperatures produced by CO2, can dramatically snowball once enough water vapour is produced as not only will it further increase global temperatures, but it also has the potential to affect weather patterns. Therefore: It is….and it isn’t. Either way, the more CO2 and methane we produce, the more water vapour will be in our atmosphere to further heat our planet – so it’s really important we dramatically reduce our CO2 emissions.