Scientist don't absolutely know what the climate is going to do just like your weatherman can't always get the forecast right. All they can do is gather up historical data about the weather and bunch of scientific measurements about how things currently are. They feed all of this information into supercomputers to create fancy charts and simulations. THEN THEY TAKE AN EDUCATED GUESS. So they may be right or they may be wrong. But, they will be confident about their answers.
Because the temperature is warming. We know that because the temperature record over the past 100 years shows warming. There are some who complain about that, but glaciers around the world are shrinking. We can think of glaciers as nature's recording thermometers. When it's colder, the snow melts more slowly and the glacier gets bigger. When it's hotter, then more ice melts than is replaced by the winter snow. Here's the thermometer:
http://nrmsc.usgs.gov/repeatphoto/
Okay, now we know it's warming. Some will say that we're starting a new ice age, and it'll start cooling soon. That's not true. Here's why ice ages occur:
http://en.wikipedia.org/wiki/Milankovitc...
In the graph, note how ice age cycles line up with eccentricity cycles.
There's near unanimous consent in the scientific community that the increased CO2 in the atmosphere is causing warming. Here's an article that talks about the increase in CO2:
http://scrippsco2.ucsd.edu/research/atmo...
Okay, so there's more CO2 and we know that it's warming. How are they related? Here's the science:
http://www.rkm.com.au/ANIMATIONS/carbon-... <== here's the physics.
http://web4.audubon.org/globalwarming/im... <== this is why CO2 is a problem.
http://www.rsc.org/images/CA1_tcm18-1379... <== Word doc. Page 6 shows where H2O and CO2 intercept different wavelengths
http://upload.wikimedia.org/wikipedia/co... <== Note that CO2 intercepts a different wavelength than water. In addition, as CO2 warms the oceans, more water evaporates, increasing it's effectiveness.
http://www.school-for-champions.com/scie... <== melting of the Siberian tundra is a global warming time bomb.
http://fora.tv/2009/08/18/A_REALLY_Incon... <== This is an hour long, but is very good.
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Basic physics, direct and indirect observations, extensive study of past natural climate changes and the absence of any other forcing (cause) to explain the currently observed changes (temperature, rise in greenhouse gasses, rise in ocean heat content, diminishing of the Albedo effect, rise of sea levels due to increased ocean temperatures and water expansion, to name just a few).
The Greenhouse Effect is a very fundamental natural phenomenon without which there wouldn't be any life on earth at all as it would simply be too cold. We need certain amounts of natural greenhouse gasses in our atmosphere to keep the planet's average climate more or less the way it has been over the past 600,000 years.
Svante Arrhenius was the first scientist to argue in 1896 that adding greenhouse gasses to the atmosphere could change the earth's surface temperature and in 1917 Alexander Graham Bell wrote "[The unchecked burning of fossil fuels] would have a sort of greenhouse effect" and advocating then already the use of alternative energy sources.
Through the years, our scientific understanding of the greenhouse effect in general and greenhouse gasses in particular has greatly improved and climate and related scientists around the world now state that:
- "Warming of the atmosphere and ocean system is unequivocal."
- "It is extremely likely that human influence has been the dominant cause of observed warming since 1950..."
Those assessments were among the ones reached in the latest IPCC report which is nothing more but an extensive, multiple year analyses of the world's climate and related scientific research, reporting and peer-reviewed scientific publications.
Please note that the 'climate has always changed' used by so many others here is not a scientifically acceptable answer. Climate did not change all by itself in the past, something caused and/or triggered it (aka a forcing). By studying past events of climate change, science was able to determine what exactly were those forcings and, thus, determine if a similar forcing is to blame for the currently observed changes. None of them were found to be; in fact, one of such natural forcings should actually cool the planet slightly and slowly when the exact opposite is happening.
Perhaps by observing it changing. Now if you are talking about future climate change, that comes from basic physics which says CO2 will increase temperatures by about 1.2C, and from models which say the warming will be much higher, because they assume positive feedbacks from water vapor and clouds. If there is instead negative feedbacks, then the warming will be not much. The IPCC report acknowledges uncertainty with regards to clouds, but doesn't spend much time on it, as it would put a big hole in the whole report.
The National Academy of Science has a booklet available to download. It is a 40-page pdf available on the NAS page linked below. (The link goes to the page, not to the download.) You can also get to a series of videos from there. The videos are informative and interesting, though a bit slow. The first 18 pages of the booklet are Part I: Evidence for Human-Caused Climate Change. It is exactly the background that you are looking for.
http://nas-sites.org/americasclimatechoi...
The NAS is the association of America's greatest scientists. It was established specifically to guide Congress and the nation in matters of complex science. There is no more credible science academy in the world.
Quote by Will Happer, Princeton University physicist, former Director of Energy Research at the Department of Energy: “I had the privilege of being fired by Al Gore, since I refused to go along with his alarmism....I have spent a long research career studying physics that is closely related to the greenhouse effect....Fears about man-made global warming are unwarranted and are not based on good science. The earth's climate is changing now, as it always has. There is no evidence that the changes differ in any qualitative way from those of the past.”
But we do know that there have been no changes that are different from the past. If there were, we could pinpoint those changes in an honest way.
They have history proven from real world observations. But history is one thing. For the future all they have are computer models. Problem is that data collected from historic geological records contradict AGW alarmist theories. That is, it has been proven that CO2 concentrations increase because of global warming. It has never caused global warming. That's just 1 of 100s of major contradictions. Computer models can be programmed in a way that a predetermined output is given from many different inputs. Not only has these climate models been proven to perform in this manner not a single computer model has accurately forecast anything and those who rely on them are constantly downgrading these computer climate forecasts. It's amusing to note that in the mid 90s to early 2000s it was common that AGW alarmists to make these forecasts in shorter terms. 10-15-20-30 years but as these apocalyptic doomsday dates approached and real world observations didn't even come close to the computer climate forecasts the AGW alarmists had to downgrade the dire forecasts many, many times. Eventually these alarmists started making the computer climate models forecast 100 years into the future. LOL! It's a lot easier to con the public when the so called consequences of AGW occur after we're all dead instead of watching them never come to fruition while we are still alive.
Very simply because the climate is ALWAYS changing in some manner or other.
The "blanket" term 'climate change' covers ALL changes.
Simple science says that CO2 in our atmosphere has risen 40% since the late 1800s and is currently 400ppm as part of our total atmosphere or 0.04%
Simple science says that plants don't grow when CO2 levels in our atmosphere are at less than 150ppm or 0.015% of our atmosphere
Simple science tells us that plants grow the best when CO2 levels are between 1000ppm and 1400ppm
Simple science says that global average temperatures have risen 0.8C since the mid-1800s.
Simple science says that temperatures in the Arctic Region have been 8C to 10C warmer in the past and recently retreating Glaciers are revealing trees from 10s of thousands of years ago.
Simple politics is telling us that they didn't like the idea of oil cartels or coal miner's unions dictating our energy prices during the 70s and 80s and therefore created the Inter-Governmental Panel on Climate Change to prove CO2 emissions (fossil fuels) were driving temperatures up.
Simple "climate" science says that CO2 emissions is not linear with global temperatures but is causing Global Warming simply due to it being logarithmical when it comes to its mathematical nature and will eventually drive temperatures up in the future.
Simple science says that current global average temperatures have been going down since 1998.
Simple science says that CO2 levels have never driven temperatures up in the past
Simple science says that current temperatures are well within natural climate variability especially when science knows that we are just coming out of the LIA (Little Ice Age).
Simply because the climate is ALWAYS changing! It has nothing to do with the myth of CO2 and "greenhouse" gases, it is purely due, as the REAL scientist know, to the ever changing orbit of the planet, and gravitational effects of the other planets and the Sun on tectonic plate movement.
How do they know they aren't wrong and they know they're right? I'm just curious.
Since they are scientists they would probably know what's happening nowadays since they have all the high technology gadgets used for forecasting and comparing the data they gathered from past and present.
They really don't know. They speculate just as you and I do.
Remember, climate science is in its infancy with little that is understood and much yet to learn.
The climate is always changing, that's a given.
But the claim being made by man-made Global Warming advocates is that the planet is getting warmer and it's not. Even the IPCC has admitted that there has been no warming for 15 years.
Top climate scientists say man-made Global Warming is not happening.
The Great Global Warming Swindle
bubbles trapped in frozen glaciers which preserve atomospheric conditions thousands of years ago, There was less CO2 and other greenhouse gases in the atomosphere back then.
Well the ten warmest years in the last 132 tears have occurred in the last 16 years. Wake up and smell the climate. This didn't happen by accident
A little thing known as scientific research aka empirical observation
Because it's different than B.C.
