[coldpie]

The contribution by humans is unequivocal. If you would like to understand how we know that, take a couple hours and read the IPCC report Summary for Policymakers. It is a fascinating and relatively easy read. It also includes projections based on several different models and estimates the impact on society from those projections.

http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_...

[acqq]

Also note that the different curves of the projections don't mean that the most probable is in the middle. The highest and the worst one is under the assumptions "if we don't do anything about it" which is exactly what was done up to now!

The lowest one is "if we soon stop using the fossil fuels completely" which is not going to happen.

And to those who don't believe:

It is caused by humans: see the energy used in the last 200 years:

https://gailtheactuary.files.wordpress.com/2012/03/world-ene...

And see what it means that the "climate changed before":

https://xkcd.com/1732/

The principle the warming works is the same why you wear a coat in the winter: the coat keeps the surface temperature of your body warmer, even if the coat itself doesn't produce a new heat. A thick coat keeps you warmer than a thin one. More CO2 does the same to the Earth surface. Without the greenhouse gases the average Earth temperature would be 0°F (or -18°C) and it is 59°F (15°C). And "a few degrees more" is really a lot and awfully fast, see the xkcd drawing again.

[pbreit]

The xkcd thing is compelling except not sure the data source and I've seen conflicting data. Rest of post not compelling.

[acqq]

> I've seen conflicting data

That's called the "wishful thinking" fallacy, to which you cling to confirm your previous "investment." If we'd look at your sources of the apparent "conflicting" data, we'd be able to see that they are intentionally biased, fabricated, cherry picked or whatever. But I would be surprised that you accept that fact, on average it doesn't function that way psychologically. Which is how humans work, but not a scientific argument.

Anyway, the natural processes, unless cataclysmic, don't make such rapid changes that we experience now. The speed of the change is orders of magnitude faster now than the non-cataclysmic natural ones. It is really going to be worse than most can even imagine. Our children or grandchildren are going to hate us for not doing enough. The politicians and lobbyists who only see their own benefit will be dead and won't care.

To compare with the "good old times": the study of human DNA shows that 70000 years ago, only 2000 humans survived one extinction event:

http://news.bbc.co.uk/2/hi/science/nature/2975862.stm

And then there was no civilization infrastructure to fail, just the hunter-gatherers, ready to move.

[CWuestefeld]

Whether or not it's caused by humans isn't relevant. If it's a problem, regardless of the cause, we ought to be thinking about what we can do to avoid it or to adapt.

So I don't understand why so much of the left chooses to frame the issue in such a way that makes it contingent on that cause.

[coldpie]

Understanding the cause is key to learning how to avoid it.

[berkay]

Is it really? Would it not be easier to find consensus (hence more productive) if we were to focus on whether the climate is changing (and not why)? Determine what the impact of the climate change will be and how we should address this problem?

[coldpie]

I have to admit I'm baffled by this line of thinking. Since coal-fired power plants are a primary driver of climate change, it makes sense to stop using them in order to help avoid further contribution to climate change. If they didn't contribute to climate change, then that incentive to stop using them would not be there. Understanding the causes of climate change directly impacts what policies we implement to mitigate it.

[CWuestefeld]

If they didn't contribute to climate change

I think here's where you're going wrong. There's a difference between "is caused by" and "contributes to".

It would be internally consistent to form an argument that supposes an alternate root cause, e.g., solar activity cycles and cycles of the Earth's magnetic field. One can state that these natural problems are (hypothetically) the root cause, while still acknowledging that CO2 is a greenhouse gas and thus decreasing our CO2 emissions - even if we weren't doing anything naughty on our own - might serve to mitigate the damage expected to be caused by those long-term natural cycles.

[coldpie]

I... guess? That hypothesis conflicts with our best data and you end up at the same policy results anyway, so I'm not sure why one would prefer that roundabout method instead of simply agreeing with the scientific consensus.

[berkay]

It's not that we should not do what you're suggesting but clearly we're not able to due to political differences. I'm suggesting that we may need to take a different approach to tackle the problem that considers political realities. Trying to reduce the carbon emissions is not the only way to address the climate change, many people argue that it may no longer be sufficient anyway. Suggestion is to focus on the fact that it's happening and try to find ways to reverse it, mitigate it's impact etc.

[graeme]

The impacts i clude the possibility of humans being literally unable to survive on some parts of the globe if wet bulb temperatures become high enough. And a constantly shifting coastline requiring recomstruction of the coastline every decade.

That's if we keep burning all the carbon. Yes, causes are important.

[gavinpc]

> consensus

So you're saying that we need consensus to do things now? My sides are splitting.

Can you name a thing that you think we have "consensus" about?

edit: and wait... "easier to find consensus"! I admit you lost me there. We just don't live in the same world. Do we have consensus for the policies we have now? So what is the justification for favoring them?

[pbreit]

The warming part is much clearer than the anthropomorphic part.

[acqq]

Even if it's maybe not clear to you or to those you like to believe, it's still clear to the relevant scientists of the whole world.

"Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to total radiative forcing is caused by the increase in the atmospheric concentration of CO2 since 1750 (see Figure SPM.5). {3.2, Box 3.1, 8.3, 8.5"

"Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system. {2–14}"

http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_...

The politicians, lobbyists and the media aren't the same as the scientists.