10 empirical evidence that humans are causing global warming – James Wight

10 Indicators of a Human Fingerprint on Climate Change

The NOAA State of the Climate 2009 report is an excellent summary of the many lines of evidence that global warming is happening. Acknowledging the fact that the planet is warming leads to the all important question – what’s causing global warming? To answer this, here is a summary of the empirical evidence that answer this question. Many different observations find a distinct human fingerprint on climate change:

10 Indicators of a Human Fingerprint on Climate Change

To get a closer look, click on the pic above to get a high-rez 1024×768 version (you’re all welcome to use this graphic in your Powerpoint presentations). Or to dig even deeper, here’s more info on each indicator (including links to the original data or peer-reviewed research):

  1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere every year (CDIAC). Of course, it could be coincidence that CO2 levels are rising so sharply at the same time so let’s look at more evidence that we’re responsible for the rise in CO2 levels.
  2. When we measure the type of carbon accumulating in the atmosphere, we observe more of the type of carbon that comes from fossil fuels (Manning 2006).
  3. This is corroborated by measurements of oxygen in the atmosphere. Oxygen levels are falling in line with the amount of carbon dioxide rising, just as you’d expect from fossil fuel burning which takes oxygen out of the air to create carbon dioxide (Manning 2006).
  4. Further independent evidence that humans are raising CO2 levels comes from measurements of carbon found in coral records going back several centuries. These find a recent sharp rise in the type of carbon that comes from fossil fuels (Pelejero 2005).
  5. So we know humans are raising CO2 levels. What’s the effect? Satellites measure less heat escaping out to space, at the particular wavelengths that CO2 absorbs heat, thus finding “direct experimental evidence for a significant increase in the Earth’s greenhouse effect”. (Harries 2001Griggs 2004Chen 2007).
  6. If less heat is escaping to space, where is it going? Back to the Earth’s surface. Surface measurements confirm this, observing more downward infrared radiation (Philipona 2004,Wang 2009). A closer look at the downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion that “this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.” (Evans 2006).
  7. If an increased greenhouse effect is causing global warming, we should see certain patterns in the warming. For example, the planet should warm faster at night than during the day. This is indeed being observed (Braganza 2004Alexander 2006).
  8. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere, otherwise known as the stratosphere. This is exactly what’s happening (Jones 2003).
  9. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratophere) cooling, another consequence is the boundary between the troposphere and stratophere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed (Santer 2003).
  10. An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in response to greenhouse warming. This has been observed by satellites (Laštovi?ka 2006).

Science isn’t a house of cards, ready to topple if you remove one line of evidence. Instead, it’s like a jigsaw puzzle. As the body of evidence builds, we get a clearer picture of what’s driving our climate. We now have many lines of evidence all pointing to a single, consistent answer – the main driver of global warming is rising carbon dioxide levels from our fossil fuel burning.

Skeptic Arguments and What the Science Says

Here is a summary of skeptic arguments, sorted by recent popularity vs what science says. Note that the one line responses are just a starting point – click the response for a more detailed response. You can also view them sorted by taxonomy, in a print-friendly version, or with fixed numbers you can use for permanent references.

  Skeptic Argument vs What the Science Says
1 “It’s the sun” The sun’s output has barely changed since 1970 and is irrelevant to recent global warming.
2 “Climate’s changed before” Climate reacts to whatever forces it to change at the time; humans are now the dominant forcing.
3 “There is no consensus” 97% of climate experts agree humans are causing global warming.
4 “It’s cooling” The last decade 2000-2009 was the hottest on record.
5 “Models are unreliable” Models successfully reproduce temperatures since 1900 globally, by land, in the air and the ocean.
6 “Temp record is unreliable” The warming trend is the same in rural and urban areas, measured by thermometers and satellites.
7 “It hasn’t warmed since 1998” 2005 was the hottest year globally, and 2009 the second hottest.
8 “Ice age predicted in the 70s” The vast majority of climate papers in the 1970s predicted warming.
9 “We’re heading into an ice age” Worry about global warming impacts in the next 100 years, not an ice age in over 10,000 years.
10 “Antarctica is gaining ice” Satellites measure Antarctica losing land ice at an accelerating rate.
11 “CO2 lags temperature” Recent CO2 increase has caused recent warming without any time lag.
12 “It’s not bad” Negative impacts of global warming on agriculture, health & environment far outweigh any positives.
13 “Al Gore got it wrong” Al Gore book is quite accurate, and far more accurate than contrarian books.
14 “1934 – hottest year on record” 1934 was one of the hottest years in the US, not globally.
15 “It’s freaking cold!” A local cold day has nothing to do with the long-term trend of increasing global temperatures.
16 “It’s cosmic rays” Cosmic rays show no trend over the last 30 years & have had little impact on recent global warming.
17 “Hurricanes aren’t linked to global warming” There is increasing evidence that hurricanes are getting stronger due to global warming.
18 “Hockey stick is broken” Recent studies agree that recent global temperatures are unprecedented in the last 1000 years.
19 “Mars is warming” Mars is not warming globally.
20 “Arctic icemelt is a natural cycle” Thick arctic sea ice is undergoing a rapid retreat.
21 “It’s Urban Heat Island effect” Urban and rural regions show the same warming trend.
22 “It’s a 1500 year cycle” Ancient natural cycles are irrelevant for attributing recent global warming to humans.
23 “Sea level rise is exaggerated” A variety of different measurements find steadily rising sea levels over the past century.
24 “Water vapor is the most powerful greenhouse gas” Rising CO2 increases atmospheric water vapor, which makes global warming much worse.
25 “‘Climategate’ CRU emails suggest conspiracy” Several investigations have cleared scientists of any wrongdoing in the media-hyped email incident.
26 “Greenland was green” Other parts of the earth got colder when Greenland got warmer.
27 “Other planets are warming” Mars and Jupiter are not warming, and anyway the sun has recently been cooling slightly.
28 “Human CO2 is a tiny % of CO2 emissions” The natural cycle adds and removes CO2 to keep a balance; humans add extra CO2 without removing any.
29 “Oceans are cooling” The most recent ocean measurements show consistent warming.
30 “Climate sensitivity is low” Net positive feedback is confirmed by many different lines of evidence.
31 “CO2 effect is weak” The strong CO2 effect has been observed by many different measurements.
32 “It cooled mid-century” Mid-century cooling involved aerosols and is irrelevant for recent global warming.
33 “Glaciers are growing” Most glaciers are retreating, posing a serious problem for millions who rely on glaciers for water.
34 “We’re coming out of the Little Ice Age” The sun was warming up then, but the sun hasn’t been warming since 1970.
35 “There’s no empirical evidence” There are multiple lines of direct observations that humans are causing global warming.
36 “IPCC is alarmist” The IPCC summarizes the recent research by leading scientific experts.
37 “Extreme weather isn’t caused by global warming” Extreme weather events are being made more frequent and worse by global warming.
38 “It warmed before 1940 when CO2 was low” Early 20th century warming is due to several causes, including rising CO2.
39 “Satellites show no warming in the troposphere” The most recent satellite data show that the earth as a whole is warming.
40 “Polar bear numbers are increasing” Polar bears are in danger of extinction as well as many other species.
41 “Mt. Kilimanjaro’s ice loss is due to land use” Most glaciers are in rapid retreat worldwide, notwithstanding a few complicated cases.
42 “CO2 is not a pollutant” Excess CO2 emissions will lead to hotter conditions that will stress and even kill crops.
43 “Greenland is gaining ice” Greenland on the whole is losing ice, as confirmed by satellite measurement.
44 “There’s no correlation between CO2 and temperature” There is long-term correlation between CO2 and global temperature; other effects are short-term.
45 “CO2 was higher in the past” When CO2 was higher in the past, the sun was cooler.
46 “Scientists can’t even predict weather” Weather and climate are different; climate predictions do not need weather detail.
47 “There’s no tropospheric hot spot” We see a clear “short-term hot spot” – there’s various evidence for a “long-term hot spot”.
48 “Animals and plants can adapt to global warming” Global warming will cause mass extinctions of species that cannot adapt on short time scales.
49 “Medieval Warm Period was warmer” Globally averaged temperature now is higher than global temperature in medieval times.
50 “Ocean acidification isn’t serious” Past history shows that when CO2 rises quickly, there was mass extinctions of coral reefs.
51 “Neptune is warming” And the sun is cooling.
52 “It’s Pacific Decadal Oscillation” The PDO shows no trend, and therefore the PDO is not responsible for the trend of global warming.
53 “Jupiter is warming” Jupiter is not warming, and anyway the sun is cooling.
54 “2009-2010 winter saw record cold spells” A cold day in Chicago in winter has nothing to do with the trend of global warming.
55 “CO2 effect is saturated” Direct measurements find that rising CO2 is trapping more heat.
56 “Greenland ice sheet won’t collapse” When Greenland was 3 to 5 degrees C warmer than today, a large portion of the Ice Sheet melted.
57 “2nd law of thermodynamics contradicts greenhouse theory” The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.
58 “Arctic sea ice is back to normal” Thick arctic sea ice is in rapid retreat.
59 “Volcanoes emit more CO2 than humans” Humans emit 100 times more CO2 than volcanoes.
60 “Pluto is warming” And the sun has been recently cooling.
61 “It’s the ocean” The oceans are warming and moreover are becoming more acidic, threatening the food chain.
62 “CO2 measurements are suspect” CO2 levels are measured by hundreds of stations across the globe, all reporting the same trend.
63 “It’s El Niño” El Nino has no trend and so is not responsible for the trend of global warming.
64 “It’s aerosols” Aerosols have been masking global warming, which would be worse otherwise.
65 “Solar Cycle Length proves its the sun” The sun has not warmed since 1970 and so cannot be driving global warming.
66 “Less than half of published scientists endorse global warming” Around 97% of climate experts agree that humans are causing global warming.
67 “Dropped stations introduce warming bias” If the dropped stations had been kept, the temperature would actually be slightly higher.
68 “CO2 has a short residence time” Excess CO2 from human emissions has a long residence time of over 100 years
69 “It’s not happening” Recent global warming is occurring and is due to humans.
70 “500 scientists refute the consensus” Around 97% of climate experts agree that humans are causing global warming.
71 “It’s microsite influences” Microsite influences on temperature changes are minimal; good and bad sites show the same trend.
72 “It’s a climate regime shift” There is no evidence that climate has chaotic “regimes” on a long-term basis.
73 “IPCC were wrong about Himalayan glaciers” Glaciers are in rapid retreat worldwide, despite 1 error in 1 paragraph in a 1000 page IPCC report.
74 “Humans are too insignificant to affect global climate” Humans are small but powerful, and human CO2 emissions are causing global warming.
75 “Greenhouse effect has been falsified” The greenhouse effect is standard physics and confirmed by observations.
76 “Mike’s Nature trick to ‘hide the decline'” Michael Mann was quoted out of context, and nothing was hidden.
77 “It’s land use” Land use plays a minor role in climate change, although carbon sequestration may help to mitigate.
78 “The science isn’t settled” That human CO2 is causing global warming is known with high certainty & confirmed by observations.
79 “Sea level rise predictions are exaggerated” Sea level rise is now increasing faster than predicted due to unexpectedly rapid ice melting.
80 “It’s methane” Methane plays a minor role in global warming but could get much worse if permafrost starts to melt.
81 “Naomi Oreskes’ study on consensus was flawed” Benny Peiser, the Oreskes critic, retracted his criticism.
82 “CO2 is coming from the ocean” The ocean is absorbing massive amounts of CO2, and is becoming more acidic as a result.
83 “Ice isn’t melting” Ice is melting at an accelerating rate at both poles and in glaciers all over the world.
84 “CO2 is not increasing” CO2 is increasing rapidly, and is reaching levels not seen on the earth for millions of years.
85 “Phil Jones says no global warming since 1995” Phil Jones was misquoted.
86 “Hansen’s 1988 prediction was wrong” Jim Hansen had several possible scenarios; his mid-level scenario B was right.
87 “IPCC overestimate temperature rise” Monckton used the IPCC equation in an inappropriate manner.
88 “It’s not us” Multiple sets of independent observations find a human fingerprint on climate change.
89 “Lindzen and Choi find low climate sensitivity” Lindzen and Choi’s paper is viewed as unacceptably flawed by other climatologists.
90 “Record snowfall disproves global warming” Warming leads to increased evaporation and precipitation, which falls as increased snow in winter.
91 “It’s albedo” Albedo change in the Arctic, due to receding ice, is increasing global warming.
92 “Springs aren’t advancing” Hundreds of flowers across the UK are flowering earlier now than any time in 250 years.
93 “Over 31,000 scientists signed the OISM Petition Project” The ‘OISM petition’ was signed by only a few climatologists.
94 “The sun is getting hotter” The sun has just had the deepest solar minimum in 100 years.
95 “Solar cycles cause global warming” Over recent decades, the sun has been slightly cooling & is irrelevant to recent global warming.
96 “IPCC were wrong about Amazon rainforests” The IPCC statement on Amazon rainforests was correct, and was incorrectly reported in some media.
97 “It’s waste heat” Greenhouse warming is adding 100 times more heat to the climate than waste heat.
98 “Water levels correlate with sunspots” This detail is irrelevant to the observation of global warming caused by humans.
99 “CO2 is not the only driver of climate” CO2 is the main driver of climate change.
100 “The IPCC consensus is phoney” Ironically, it’s those who are mispresenting Hulme’s paper that are the ones being misleading.
101 “Trenberth can’t account for the lack of warming” Trenberth is talking about the details of energy flow, not whether global warming is happening.
102 “Climate is chaotic and cannot be predicted” Weather is chaotic but climate is driven by Earth’s energy imbalance, which is more predictable.
103 “Mauna Loa is a volcano” The global trend is calculated from hundreds of CO2 measuring stations and confirmed by satellites.
104 “CO2 emissions do not correlate with CO2 concentration” That humans are causing the rise in atmospheric CO2 is confirmed by multiple isotopic analyses.
105 “Breathing contributes to CO2 buildup” By breathing out, we are simply returning to the air the same CO2 that was there to begin with.
106 “Tree-rings diverge from temperature after 1960” This is a detail that is complex, local, and irrelevant to the observed global warming trend.
107 “A drop in volcanic activity caused warming” Volcanoes have had no warming effect in recent global warming – if anything, a cooling effect.
108 “Water vapor in the stratosphere stopped global warming” This possibility just means that future global warming could be even worse.
109 “Scientists retracted claim that sea levels are rising” The Siddall 2009 paper was retracted because its predicted sea level rise was too low.
110 “Southern sea ice is increasing” Antarctic sea ice has grown in recent decades despite the Southern Ocean warming at the same time.
111 “Antarctica is too cold to lose ice” Glaciers are sliding faster into the ocean because ice shelves are thinning due to warming oceans.
112 “It’s ozone” Ozone has only a small effect.
113 “Global temperatures dropped sharply in 2007” But global temperatures rose sharply in 2009, to the second hottest level.
114 “It’s CFCs” CFCs contribute at a small level.
115 “CO2 was higher in the late Ordovician” The sun was much cooler during the Ordovician.
116 “Melting ice isn’t warming the Arctic” Melting ice leads to more sunlight being absorbed by water, thus heating the Arctic.
117 “Warming causes CO2 rise” Recent warming is due to rising CO2.
118 “It’s satellite microwave transmissions” Satellite transmissions are extremely small and irrelevant.
119 “It’s global brightening” This is a complex aerosol effect with unclear temperature significance.
120 “Greenland has only lost a tiny fraction of its ice mass” Greenland’s ice loss is accelerating & will add metres of sea level rise in upcoming centuries.
121 “Satellite error inflated Great Lakes temperatures” Temperature errors in the Great Lakes region are not used in any global temperature records.
122 “We didn’t have global warming during the Industrial Revolution” CO2 emissions were much smaller 100 years ago.
123 “Royal Society embraces skepticism” The Royal Society still strongly state that human activity is the dominant cause of global warming.
124 “Positive feedback means runaway warming” Positive feedback won’t lead to runaway warming; diminishing returns on feedback cycles limit the amplification.


Many thanks to Dr. Jan Dash, Director of the UU-UNO’s Climate Portal for writing many of the one line responses in ‘What the Science Says’, with some edits by John Cook.

October 3, 2010 - Posted by | anti-kapitalizm, iklim, türcülük, doğa / hayvan özgürlüğü

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