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Is there scientific consensus on climate change?

The major scientific agencies of the United States — including the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) — agree that climate change is occurring and that humans are contributing to it. In 2010, the National Research Council concluded that "Climate change is occurring, is very likely caused by human activities, and poses significant risks for a broad range of human and natural systems". [1] Many independent scientific organizations have released similar statements, both in the United States and abroad. This doesn't necessarily mean that every scientist sees eye to eye on each component of the climate change problem, but broad agreement exists that climate change is happening and is primarily caused by excess greenhouse gases from human activities.

Scientists are still researching a number of important questions, including exactly how much Earth will warm, how quickly it will warm, and what the consequences of the warming will be in specific regions of the world. Scientists continue to research these questions so society can be better informed about how to plan for a changing climate. However, enough certainty exists about basic causes and effects of climate change to justify taking actions that reduce future risks.

What is the evidence that proves the climate is changing?

The global average temperature increased by more than 1.4°F over the last century. [2] In fact, according to the National Oceanic and Atmospheric Administration (NOAA), the decade from 2000 to 2010 was the warmest on record, and 2010 was tied with 2005 as the warmest year on record. [3] Rising global temperatures have also been accompanied by other changes in weather and climate. Many places have experienced changes in rainfall resulting in more intense rain, as well as more frequent and severe heat waves. The planet's oceans and glaciers have also experienced changes: oceans are warming and becoming more acidic, ice caps are melting, and sea levels are rising. [4] All of these changes are evidence that our world is getting warmer.

Are human activities or natural variations in climate responsible for the climate change being observed today?

The Earth does go through natural cycles of warming and cooling, caused by factors such as changes in the sun or volcanic activity. This has been closely examined, and the warming we have seen in the past 50 years cannot be explained by natural factors alone. [5] This figure illustrates one piece of evidence that shows that recent global warming is primarily a result of greenhouse gas emissions from human activities.



This figure shows the observed average global temperatures from 1900 to 2000 (black line) along with the temperature ranges predicted by climate models. The blue band shows the expected temperature range based on climate models that account only for natural forces. The pink band represents the temperature range predicted by climate models that also include emissions of greenhouse gases from human activities. The recent increase in average global temperatures aligns with the predicted temperatures from the model that includes the greenhouse gas emission.

Is climate change influenced more by human activities and excess greenhouse gases or changes in the sun's energy?

The sun has natural periods of warming and cooling. With satellites, scientists have measured fluctuations in the sun's energy and found that these recent variations have been small in comparison to human influences in the last several centuries, with no increase in solar energy in the past 50 years. [2] Thus, changes in the sun's energy cannot explain the warming we have seen over the past several decades. In contrast, the warming we are observing is consistent with the warming properties of carbon dioxide and other heat-trapping gases that we are adding to the atmosphere.

How can carbon dioxide hurt us?

Carbon dioxide is a necessary ingredient for plants to perform photosynthesis, and a critical component of our atmosphere. However, you can have too much of a good thing. The excess carbon dioxide we are adding to the atmosphere increases global temperatures, leading to climate changes that can harm plants, animals, and humans.

How can a change of one or two degrees in global average temperatures have an impact on our lives?

Changing the average global temperature by even a degree or two can lead to serious consequences around the globe. For about every 2°F of warming, we can expect to see

•5—15% reductions in the yields of crops as currently grown

•3—10% increases in the amount of rain falling during the heaviest precipitation events, which can increase flooding risks

•5—10% decreases in stream flow in some river basins, including the Arkansas and the Rio Grande

•200%—400% increases in the area burned by wildfire in parts of the western United States [6]

Global average temperatures have increased more than 1.4 degrees Fahrenheit over the last 100 years. [2] Many of the extreme precipitation and heat events that we have seen in recent years are consistent with what we would expect given this amount of warming. [5] Scientists project that Earth's average temperatures will rise between 2 and 12 degrees Fahrenheit by 2100. [1]

Do a few extra cold or snowy winters in your hometown mean that climate change is not happening?

A few extra cold or snowy winters in your hometown doesn't mean that global warming isn't happening. We know thatglobal average temperatures are rising. However, even with this global warming, at the local or regional level, we can expect to have some colder-than-average seasons or even colder-than-average years. For example, in the Eastern United States, the winters of 2010 and 2011 were colder than the average winters from the previous decades. In fact, extra snowy winters can be expected. In a warmer climate, more water vapor is held in the atmosphere causing more intense rain and snow storms. As the climate warms, we do expect the duration of the snow season to decrease — however, as long as it is still cold enough to snow, a warming climate can lead to bigger snowstorms. [5]

Do emissions of carbon dioxide from human activities have a big impact on Earth's climate?

Plants, oceans, and soils release and absorb large quantities of carbon dioxide as a part of the Earth's natural carbon cycle. These natural emissions and absorptions of carbon dioxide on average balance out over time. However, the carbon dioxide from human activities is not part of this natural balance. Ice core measurements reveal that carbon dioxide levels in the atmosphere are higher than they have been for at least 800,000 years. [5] The global warming that has been observed in recent decades was caused by elevated levels of carbon dioxide and other greenhouse gases in the atmosphere, due primarily to human activities.[1]

In the past, has Earth been warmer than it is today? If so, does that mean we shouldn't worry about global warming?

There were times in the distant past when Earth was warmer than it is now. However, human societies have developed and thrived during the relatively stable climate that has existed since the last ice age. Due to excess carbon dioxide pollution, the climate is no longer stable and is instead projected to change faster than at any other time in human history. This rapid climate change will expose people to serious risks. Sea level rise, increasing droughts and wildfires in some regions and increasing flooding in others, more heat waves, and other effects of climate change all pose risks to human health, infrastructure critical to our homes, roads, and cities, and the ecosystems that support us. [5]

Will a small rise in sea level affect people (even in the United States)?

A small rise in sea level will affect many people, even in the United States. The amount of sea level rise expected to occur as a result of climate change will increase the risk of coastal flooding for millions to hundreds of millions of people around the world, many of whom would have to permanently leave their homes. [7] Global sea level has risen approximately 9 inches, on average, in the last 140 years. [4] This has already put some coastal homes, beaches, roads, bridges, and wildlife at risk. [5] By the year 2100, sea level is expected to rise another 1.5 to 3 feet. [6] Rising seas will make coastal storms and the associated storm surges more frequent and destructive. For example, in New York City what is currently termed a once-in-a-century coastal flooding event could occur as frequently as once per decade. [5]

Are the temperature records showing global warming is happening reliable?

Multiple temperature records from all over the world have all shown a warming trend, and these records have been deemed reliable by the National Aeronautics and Space Administration (NASA), and the National Oceanic and Atmospheric Administration (NOAA), among others. [8] Other observations that point to higher global temperature includes: warmer oceans, melting arctic sea ice and glaciers, sea level rise, increasing precipitation, and changing wind patterns. [4] http://epa.gov/climatechange/facts.html]
Now, Rap and those like him will most likely say "all that is bullshit" BECAUSE the source is the EPA (which of course to them reads "government=Obama=can't-be-right"). To which I say: Show us verifiable data that refutes what is stated in that quote; the source means nothing if you cannot refute what it states. Which will, of course, mean nothing to them, and we know where it goes from there.

But I offered it, and at the site there are references and details enough to make your head spin. If our deniers would actually bother to READ what's there, check the references, look at the charts and graphs and backup data, it might mean something to them. Which we know they will not. Most likely, if they bother to do anything but snark, they will hunt around for SOME kind of data to negate what's offered, and I'm sure they'll find it, by at least one "scientist".

Nonetheless, there is, in "white and black", the simplest and most comprehensive explanation of the issue one can easily locate, period. And it only took a few minutes.

Leaving America aside, and thinking in terms of SCIENCE, try this on for size:

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97% of climate experts agree humans are causing global warming.

Science achieves a consensus when scientists stop arguing. When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science). Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

But the testing period must come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory. When Russian scientist Dmitri Mendeleev constructed his periodic table of elements, not only did he fit all known elements successfully, he predicted that elements we didn’t even know about would turn up later on – and they did!

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other's work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted - and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them. A survey of all peer-reviewed abstracts on the subject 'global climate change' published between 1993 and 2003 shows that not a single paper rejected the consensus position that global warming is man caused. 75% of the papers agreed with the consensus position while 25% made no comment either way, focusing on methods or paleoclimate analysis (Oreskes 2004).

Several subsequent studies confirm that “...the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes”. (Doran 2009). In other words, more than 95% of scientists working in the disciplines contributing to studies of our climate, accept that climate change is almost certainly being caused by human activities.

We should also consider official scientific bodies and what they think about climate change. There are no national or major scientific institutions anywhere in the world that dispute the theory of anthropogenic climate change. Not one.

In the field of climate science, the consensus is unequivocal: human activities are causing climate change. http://www.skepticalscience.com/global-warming-scientific-consensus.ht
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I rest my case.