Summary of how Climatologists know Global Warming could be catastrophic.
PROOF 1. Despite regional variations, the overall mean temperature of the earth is rising. This is confirmed by:
--weather station data going back to 1880
--satellite data going back to 1979
--balloon data going back to the 1960s
Here is NASA's weather station data which shows the strong slope upwards of global temperature.
Notice the strong temperature upward trend.
Climate models (that use as inputs solar radiation, global warming gases, deforestation, aerosols (including volcanic eruptions)) -- can explain -- using PHYSICS equations -- global average temperature. These can explain the last 130 years of data collected from land weather station data.
When all the forcings are combined in Figure 6, the net forcing shows good approximation of global temperature going back to 1880. There is still internal variability superimposed on the temperature record due to short term cycles like ENSO.
PROOF 2. We have used proxies (bore holes, tree rings, and most important - ice cores) to measure the long term temperature and concluded, while global mean temperature is relatively stable over time: The difference between the Little Ice Age of the 1600s and today is only about 1 ½ degree Centigrade. This is why a 1-2 degree global mean increase is HUGE!!
Proxies also show it is likely hotter now than thousands of years in the past.
The long term ice cores show there are natural cycles approximately 120,000 years in length, broken by short warm periods called interglacials. These Milankovitch natural cycles are thought to be primarily due to long term changes in the Earth's orbit flavor that affect how much sunlight hits the earth.
Notice the ice cores show a 95+% long term correlation of temperature with CO2:
Below is a picture from the Vostok ice core. The blue line is the temperature; the green line is CO2.
Here is the mechanism: When there is an initial increase in sunlight from Milankovitch cycles - this triggers an initial warming which warms the oceans and melts ice sheets. After a few hundred years this releases more CO2. The extra CO2 in the atmosphere causes further warming for 99% of the cycle.
When the Milankovitch cycle switches to cooling, the reverse happens.
We are in a COOLING phase of the Milankovitch cycles right now, but temperatures have been increasing.
PROOF 3. We know our warming cycle is not natural (Milankovitch) and not due to the sun because of the following:
A study by Usoskin (2008) is considered the definitive study on solar activity.
"Solar Activity over the last 1150 years - Does it Correlate with Temperature?"
In summary he says yes there is a correlation with a very high (95%) confidence rate between sunspot number index and proxies of solar irradiance from as far back as 850 AD to 1975. However after 1975, this correlation breaks down completely.
"During these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown and significant trend, so that at least this most recent warming episode (since 1975) must have another source." [which Usoskin has said elsewhere is likely Co2 warming. )
MORE IMPORTANT: There are other clues the warming we have experienced in previous decades is from CO2 and not from the sun:
(i) The sun has been flat in terms of irradiance for the past 50 years.
-- But the average global temperature has been warming.
(ii) If it were the sun causing the warming: Increased sunlight would heat the stratosphere first, where the ozone layer absorbs solar ultraviolet light.
-- But the stratosphere is cooling (as predicted by CO2 radiative warming)
(iii) Increased sunlight would heat the equator more than the poles (Lambert's cosine law).
- Instead we see "polar amplification," (read more for details on the site)
(iv) Increased sunlight would increase daytime temperatures more than nighttime temperatures.
-- But nighttime temperatures have risen more, which is consistent with an atmosphere of increased IR opacity holding in surface warmth better. Think of the way a cloudy night is warmer than a clear night.
(v) Increased sunlight would increase summer temperatures more than winter temperatures.
-- But winter temperatures have risen more. Again, more greenhouse gases hold in the heat better when sunlight is decreased.
see more details here
http://BartonPaulLevenson.com/Sun.html who gets it from the IPCC.
PROOF 4. We have the evidence that our glaciers and both poles are melting.
ARCTIC - The ice in the Arctic is about half now about what it was 30 years ago (as measured by satellites); and most of it is "new" ice; not old ice.
NASA's Grace satellite show that Antarctica has been losing more than a hundred cubic kilometers (24 cubic miles) of ice each year since 2002 and at an accelerating rate, too. How is it possible for surface melting to decrease, but for the continent to lose mass anyway? The answer boils down to the fact that ice can flow without melting.
GLACIERS: Glaciers are melting around the world
"There is no doubt that most mountain glaciers are shrinking worldwide in response to a warming climate."
Here is a Wikipedia link that compiles the dramatic global loss in glaciers.
Here is a description of the worldwide loss of glaciers around the world.
PROOF 5. CO2 levels have increased 40% since the Industrial Age and are now at the highest levels since at least 400,000 years [i.e., are higher than any shown in the ice cores].
Lab studies have validated that CO2 has a warming effect as a greenhouse gas.
We also have strong evidence CO2 has a warming effect by looking at our own solar system.
The planet Venus is hotter than Mercury, even though Mercury is closer to the sun, because of CO2. [The equations that estimate planetary history can be used fairly accurately to apply to Venus and Mars as well as the Earth.]
Remember the high correlation in the ice cores between CO2 and temperature?
--Notice we are at much higher levels now of CO2, but the warming hasn't hit yet. Scientists think it is indirect FEEDBACKS from extra CO2 in effect that could make warming catastrophic. Here is why:
-- the ice caps are melting-- NASA and NOAA satellites confirm it.
The ice acts to reflect sunlight back into space, therefore more heat will be absorbed by the Earth (temperatures will increase substantially), when the ice has fully melted.
--underneath the ice are LARGE deposits of methane. Methane is a more powerful global warming gas, than CO2 that will now be released into the atmosphere.
--warming from CO2 means the atmosphere can hold more water vapor (another global warming gas); Because there are more clouds, this creates more powerful weather systems -- including in some areas more rain AND more snow (clouds shut out sunlight)
-- the oceans are currently absorbing around 80% of the additional CO2 from human causes. This is creating problems with the corals and algae in higher latitudes now and studies indicate will creep into lower attitudes. In addition, there is concern that the oceans will saturate and start releasing more CO2 into the atmosphere.
Then of course the additional CO2 is creating acidification of the ocean waters, and many coral species and other plankton life will die from this, affecting the food chain. And it is happening so rapidly, scientists worry if new species will have enough time to develop or not.
PROOF 6. We also know we are emitted more CO2 because the oceans are more acidic and already creating problems.
--The chemistry of the oceans is changing faster than it has in at least the last 800,000 years because of the carbon dioxide being absorbed from the atmosphere, according to the National Research Council an arm of the National Academy of Science. The RATE of change "exceeds any known change in ocean chemistry for at least 800,000 years," the report said.
Ocean Dead-Zones May Be Linked To Global Warming
A review of all available ocean data records concludes that the low-oxygen events which have plagued the Pacific Northwest coast since 2002 are unprecedented in the five decades prior to that, and may well be linked to the stronger, persistent winds that are expected to occur with global warming.
Plankton may not be able to adapt to the acidic conditions of the oceans
Furthermore, our simulations show higher rates of environmental change at the surface for the future than the Palaeocene-Eocene thermal maximum, which could potentially challenge the ability of plankton to adapt.
High temperatures have already destroyed some coral reefs
Sound like the type of world you want your children to inherit?