We are weeks away from the much-anticipated release of the 5th climate report from the Intergovernmental Panel on Climate Change (IPCC). This organization has worked very hard to summarize the latest science on climate change, with thousands of donated hours from scientists around the globe. Although there are many other climate reports that synthesize the science, the IPCC is the largest and most comprehensive.

I know many of the scientists who have taken on leadership author roles, without pay, to produce this document. We owe them our gratitude and congratulations.

So, what will the report say? I will admit that I have not read the report (it hasn’t been released). Early drafts have been leaked, primarily by people trying to disrupt the process. These early drafts allow us to predict what will be contained within the report. An alternative approach is to review the immense body of literature from which the report is drawn. Based on the literature I’ve reviewed, I will predict the central themes of the IPCC report.

First, readers will likely find that this report is very similar to the last report (which was released in 2007). There will be slight changes to our confidence in certain observations. Climate models will have improved slightly, particularly in how they handle atmospheric particulates and cloud formation. A major effort since the last report has been the use of climate models to predict changes at the regional level. The report will likely say that this endeavor has had mixed success.

The new report will describe how climate changes are continuing without abatement. In particular, temperatures are rising, oceans are heating, waters are rising, ice is melting, the oceans are acidifying, heat is even moving to the deepest parts of the oceans. Just as importantly, the report will show that these changes are largely human-caused.

Some items are worse than we thought. In the last report, ice loss, particularly from Greenland, was a minor issue. Now, it is clear that not only Greenland, but also Antarctica are melting and this melt is raising sea levels. Furthermore, Arctic sea ice is being lost faster than previously reported.

The new report will likely have continued questions. For instance, how will hurricanes change in a warming world (the most powerful hurricanes are becoming even more powerful, but the change in frequency is not known) is still an open question.

Extreme weather will be a mixed bag. Some extreme weather has certainly increased (heat waves for instance, drought in certain areas, and heavy precipitation events). Changes to tornadoes and thunderstorms? That is one area that is highly uncertain.

So, in short, since 2007 we have developed better tools, and we are more certain about how we are changing the climate. Other areas still vex us. But, it is clear we certainly know enough to take action to stop the coming changes to our climate.

How does this square with my title? One continuing question is, how much and how fast will the climate change. Are we going to be in a “slow simmer” or a “fast boil”? The answer to this question rests on how sensitive the climate is. If the climate is not very sensitive, it means the Earth’s temperature will change more slowly. A more sensitive Earth will have a more rapid temperature change.

There is some belief that the IPCC will lower the range of climate sensitivity by a tiny amount. If my crystal ball is correct, the denialosphere will latch onto this, and will, unwittingly, be agreeing that the IPCC is correct; we are changing the climate. You cannot both accept the IPCC conclusions that humans are changing the climate and simultaneously claim that climate change is either not occurring or is natural. In the end, the contrarians will be in the “slow simmer” camp. So listen carefully to the Christopher Moncktons, James Inhofes, and Rush Limbaughs of this world. Wait for them to bring up the IPCC sensitivity and realize just how much they have conceded.

But back to the IPCC; in a certain sense, the IPCC has done its job. For this fifth report, they have synthesized the science and provided enough evidence that action is warranted. How many more reports of this type do we need? Will a sixth report that confirms what we already know make much of a difference? Will a seventh? Do these reports need to be written every 5-6 years? Perhaps one a decade would be sufficient? These reports require enormous amounts of time and energy. Scientists who take authorship roles put their own research on hold, sometimes for years.

Whatever the future holds for the IPCC, the history books will tell us we were warned. Time and time again, the world’s best scientists have sent us clear messages. Whatever happens, whatever pathway we choose, whatever are the future climate disruptions, we owe these scientists, and the IPCC our deepest gratitude. Thanks.