People are always looking for grants and publicity gets grants (witness Horner's 'TRex as scavenger' theory, which is unsupported by any rational review of the evidence.) The 'back-and-forth', to the extent that its going on, is wrong.
"No one is denying the Chicxulub happened or that it had a significant influence, but there is apparent evidence that some dinosaurs survived for a significant period of time after the impact."
Really? Citations please? Don't have any? Could it be because there are none? People have looked for any evidence of dinosaur survival past K-T for a hundred years and have found - NONE. Zip. (Except for 'Avian Dinosaurs', of course, better known as birds.)
"Furthermore, for about 1 million years prior to the impact, the Deccan Trap volcanism was taking place (India was passing over the Reunion hotspot, see map below) and that apparently had a global climate effect, too."
Thats right, it was. And there is no evidence that it affected dino-diversity prior to the end of the Cretaceous.
"So, though the interpretation is tentative, it appears that climate change set up the dinosaurs for a fall, Chicxulub pushed most of them over the edge, and continuing climate change finished off the remnant survivors."
Wrong. The Chixculub impact killed off all the dinosaurs within a fortnight in all probability. At least that is what all the evidence indicates. Most people have no idea of the devastating impact on life that an asteroid the size of Manhattan Island hitting the earth would cause. The surface of the entire North American continent was literally incinerated within an hour due to the angle of the asteroid's impact and the subsequent direction of the ejecta from the impact point. The rest of the world was done within a few days at most. I'd suggest this link for the text of a New Scientist article of a few years back titled "Fires of the Apocalypse": http://www.exodus2006.com/fires.htm
"CO2 concentration peaked for the Mesozoic at about the beginning of the Cretaceous (approx. 6x modern) and declined through the period; it was close to modern at the K/T boundary."
I was talking about measured temperature variations, not CO2 levels. Those variations have continued throughout earth's history right up to the present day and in fact, looking at that data, we have still not 'warmed up' fully since the last Ice Age. For man to think that he can have a large impact on same is the ultimate in hubris.
One of the main names in the debate is Gerta Keller. The short article below talks about her research:
Report Says Asteroid Did Not Kill Dinosaurs
Obviously, as you can read, other's don't agree. Regarding the Deccan Traps volcanism, this is even more recent:
India's Smoking Gun: Dino-Killing Eruptions
Here's a quote: ""In only one case is there evidence for both volcanism and impact," she said. And that is the K-T mass extinction that ended the reign of the dinosaurs. "Our view is that impact added to the stress already generated by an ongoing massive eruption, enhancing significantly the extent of the extinction, which would however have taken place even if the impact had not occurred."
This is also an interesting summary page:
The Great Chicxulub Debate concludes - where next?
The summary from Smit does a good job of covering why the Chicxulub impact theory is still very strong regarding the demise of the dinosaurs.
This is a short overview of the diversity and extinction aspect (Lectures 36-39):
The Cretaceous-Tertiary Extinction I: Definitions and Dramatis Personae
Wrong. The Chixculub impact killed off all the dinosaurs within a fortnight in all probability. At least that is what all the evidence indicates. Most people have no idea of the devastating impact on life that an asteroid the size of Manhattan Island hitting the earth would cause. The surface of the entire North American continent was literally incinerated within an hour due to the angle of the asteroid's impact and the subsequent direction of the ejecta from the impact point.
While it feels very strange to debate this -- because I'm fascinated by the Chicxulub impact and the entire discovery of the K/T boundary and subsequent evidence leading to the crater structure -- it should be pointed out that a lot of organism groups survived it. Any analysis of the extinctions also has to also take into account what survived. If one surmises that the extinction and subsequent effects preferentially affected larger organisms, then what happened to the small dinosaurs? Why did some reptile groups survive? Etc.
I don't think you and I can resolve this. Note then that I should be clear in stating that the Chicxulub impact played the major role in the extinction of the dinosaurs, at least according to what I know. But there was climate stress at the time, and I think the evidence indicates that was a contributing factor.
I was talking about measured temperature variations, not CO2 levels. Those variations have continued throughout earth's history right up to the present day and in fact, looking at that data, we have still not 'warmed up' fully since the last Ice Age. For man to think that he can have a large impact on same is the ultimate in hubris.
Well, the Cretaceous was cooler than the Triassic and Jurassic, but both climate regimes were warmer than present, which is consistent with the much higher atmospheric CO2 concentrations.