Scientists believe that we are causing serious environmental damage that, if we do not stop, could be very dangerous to humans.
There are four problems here:
Damage to the environment has accumulated over the past 150 years. Future damage has accumulated very slowly so this point will be dangerous to people in the near future - maybe 50-100 years from now. It makes it hard to get people excited about doing anything about it today.
The timing problem is having a huge amount of momentum in these changes. If we stop all pollution today, it will be many years maybe decades before environmental recovery begins. The longer it lasts until we address this issue, the worse the problem we are creating - exacerbating the threat, making it harder to correct and more expensive. We have not stopped making it worse.
Most people do not appreciate the size of the problem. The amount of harmful emissions thrown into the air is measured in the thousands of millions of tons per year from almost every type of transportation, industry, and technology as well as dozens of natural resources. If we wait any longer, then the effort to reduce man-made emissions will cost trillions of dollars, which will take decades to make and bring about significant changes in the world economy.
Industries and technologies with the highest harmful emissions are also very profitable because they use the air (and rivers and oceans) as their disposal for their exhaust and waste at no cost to them. Combustion of fossil fuels, land use and industry provides income to the owners and stockholders (the 1% ers) of these corporations and the cost of any cleaning will reduce revenues. The 1% er bought politicians so they could continue their emissions and high incomes at the expense of the environment and the people. So far, it has stopped any attempts to address the problem.
Given # 2 and # 3 above, the longer we wait to deal with the problem, the worse the effects will be felt at some point in the future. The catastrophes you hear in the media are predictions of what could happen if we continue like today in the next 100 years. That is a very unlikely situation. We will finally act but it is true that the longer we wait, the harder it will be, the more expensive and time consuming.
However, due to # 1 and # 4, efforts to fix or even begin problem planning and assessment have made little progress other than continuing to monitor the damage done and record the earliest effects - including hope there are tipping points that will initiate various feedback loops that can suddenly accelerate and worsen the damage done.
These comments include melting sea ice, melting ice in Greenland, metafrost methane emissions, CO2 ocean emissions, ocean acidity, shutdown of ocean currents around the world, etc. Other factors that have been predicted but will rise more slowly include rising seas, migratory bugs and animals and extinction, thirst, loss of fresh water, extreme weather, etc .... but remember, these are all worst case scenario if we do not do anything to address the problem.
Boiling frog is a fable that depicts a frog slowly boiled to life. The premise is that if a frog is suddenly placed in boiling water, it will jump, but if the frog is placed in warm water and then slowly boiled, it will not know the danger and cook until it dies. The story is often used as a metaphor for the inability or unwillingness of people to react or be aware of obscene threats that appear slowly rather than abruptly.
Climate scientists are trying to tell us that there is a serious threat to our future. They try to tell us that right now, we are acting like a frog in lukewarm water and the heat is rising. Once we recognize the danger, we will also discover that the pot in which we are located is enormous and requires a great deal of effort to get out of it. The question is, "how long will we wait until we stop making it worse?".
The reality is that even without humans, climate change and global warming would still exist because of the trees. Trees make use of CO2 to protect themselves from environmental changes, it's just that humans speed ip the process way too much