What does this mean?
What evidence? (and I refer here to ''bad'' from increasing levels of co2 - (global warming in other words) not contamination, pollution, deforestation etc)
For example, what is the optimum average global temperature?
It means that in the CO2 records which have been referred to by other sceptics here and have used as evidence to prove their own arguments, those records show the natural (Gaia?) cycles of CO2 up and down between approximately 175ppm to approx 300ppm in the atmosphere.
We have moved away from that fluctuating course which has been established for at least 800,000 years, and jumped to 400ppm atmospheric CO2 in a century.
I'm gonna take a guess at your second question, you're asking why global warming due to CO2 increase is bad?
There's a whole number of ways that it will have a negative impact on not just humanity but MOST species on earth. I guess the first ones springing to mind is rising sea levels if you want to use the estimations of JUST Greenlands land-ice melting which could raise sea levels by 7m. I know that isn't necessarily expected to happen in the next hundred or hundreds of years, but that alone would displace millions of people. This again, in itself isn't necessarily a bad thing if we are prepared for it, but how do we prepare for it if governments and societies just ignore the warnings and say f**k it it's a natural cycle. Even if it IS a completely natural cycle, that doesn't refute the fact change is necessary.
The fact humanity relies on only about 50 different crop types for 90% of its calories, protein and fat... if those crops aren't modified and the areas they are grown is negatively impacted by flooding or drought, that's putting serious strain on food supplies globally. You only need to look at one bad years harvest and see how much it impacts the prices of staples like bread and rice the following year to see how it could cause major fallout if year on year crops are diminishing.
Ironically the whole start of this discussion was not just about climate change in terms of global warming and CO2, it's about how humanity is behaving as stewards of our planet. Movements like extinction rebellion aren't just trying to force change on CO2 emissions, they're trying to halt things like millions of tonnes of single use products ending up in the seas, rivers and ultimately our own food supply chains.
Stop insane amounts of pollution being dumped into waterways, unbelievable amounts of toxins bellowed into the air we breathe and so on... why would anyone even consider saying that's a dumb thing to protest against?
Halting biodiversity loss - it's incomprehensible to me that some people can't see our place in the world as being inextricably linked to the natural world around us, and not wanting to actively prevent thousands of species becoming extinct as it will inevitably have huge repercussions for us.
Even the way we farm things has moved to areas you can see from space being single crop area which are virtually barren of all other life, relying on intensive fertilisation and irrigation. That land gets consistently poorer, It's unsustainable. Deforesting millions of acres of woodland and forests, clearing out countless species and using the land to produce ONE crop and ONE species... I don't understand why anyone thinks it's in our interest in either the short or long term?
Put it this way then.
If you look past the 'global warming' and lets all just for a minute pretend it doesn't exist in anyone's mind at all... why do you disagree with the other things they are campaigning for? Cleaner air, cleaner water, preventing ecological damage and species loss, more sustainable farming practices, energy production that doesn't produce pollution, not dumping pollution into the water and air. What argument would you make against any of these things that are in everyone's interest?
