Quetzal, are you talking about global warming or something?
Partly, but not mostly. The effects of global warming/global climate change have only been modeled - and the models don't always agree. However, at the minimum, all agree that the risk of severe disruption in global weather patterns is very high. These include things like flooding in desert regions, drought in agricultural regions, increased likelihood of severe storms, etc. Not to mention the disruption in the current patterns that give us our weather today (like the Gulf Stream disappearing/moving southward because of massive influx of cold water from melting ice caps, etc). The more pertinent aspect of immediate weather problems (like the severe storms hitting the US) relates to ENSO ("El Nino-Southern Oscillation") effects. We seem to be entering another - and perhaps extreme - cycle now.
Most of what I was thinking about related to human activity: desertification caused by unsustainable land use patterns leading to famine (c.f., the Saharan rim); deforestation leading to things like increased landslide activity (and concurrent loss of human life; Google Posoltega "Hurricane Mitch" Nicaragua for a stark example), increases in pest species (like mosquitos and disease-carrying flies), and release of EIDs ("emerging infectious diseases") from hitherto unknown/untapped disease reservoirs; famine through distruction of "wild" type crop plants leading to reduced resistence in domesticated crops (with no reserve of genetic variability to draw from) and overuse of pesticides/herbicides leading to ever-more resistent strains of pathogens/phytophagous insects; and finally homogenization of the biosphere caused by bioinvasion impelled by globalization. All of these things combined leading to horrendous wars and mass deaths over competition for dwindling resources and living space.
IOW, the fundies are right: we quite likely are heading for something resembling "End Times" (if you define that to mean "the end result being a world unrecognizable by today's standards"). However, there's nothing supernatural about it. >99% can be dropped directly at the doorstep of human activity. The good news is, we CAN do something to stop/mitigate the problems. Some things we're already working on (preservation of wild strains, identification of new food crop types, etc), as well as attempting to limit some of the worst pollution-caused destruction. However, it's far from certain we'll be willing to do enough to stave off our own destruction. Great world we're leaving our children, isn't it?
And I'm not even a radical environmentalist! You should hear some of the doomsday scenarios put forward by the enviro-wackos!