This political cartoon claims to sum up the science of climate change, but what it sums up is the politics of climate change debate from a climate-change-denial point of view:
Done properly, science is rarely "settled." Research of climate change is ongoing and will be, probably, for the foreseeable future, because as new data is analyzed and old data reanalyzed with new tools, new information is revealed.
Climate change was proven to be a real phenomenon over 100 years ago by a climate researcher named Ellsworth Huntington. He did not prove global warming, nor was that his intent, but his evidence, gathered worldwide, showed that within human history and prehistory climate had changed and forced human migrations, as well as other effects. Over the course of the last century many researchers joined that field, including me, for a time.
One thing that has been known for some time is that we are in an "interglacial period." Research shows that as long as there is a continental mass covering one pole, currently Antarctica over the South Pole, there have been recurring ice ages separated by warmer periods. The question is "what drives the changes from global ice age to global warming and back again?" The science of tree-ring research, which I was involved with, began with the hypothesis that sunspot cycles appear to coincide with temperature changes and might be a causal factor. To date that causal relationship has not been confirmed, and Tree-ring scientists aren't lying that it is. Science is rarely that narrowly focused. Other data show the possibility of other relationships that are then researched.
One line of research has shown that fossil fuel use frees carbon that was trapped in the earth's crust for millions of years, and freed carbon combines with oxygen to form carbon dioxide, a known greenhouse gas. Climate researchers use weather data recorded for some time, and tree-rings are able to store data of their growth as it relates to precipitation and temperatures, and other methods of determining past climate have been developed. So now, a link has been discovered between the advent of the industrial age and subsequent warming. There is now sufficient data to support that link, strongly. Within the climate research community there is still debate only about the extent, duration, severity, and time of onset of the life changing effects.
Scientists, however, are no longer in control of the public discourse, because of politics, so the scientific finding of a link between human activity and global warming is a political "football". The politicians co-opt whatever they can to bring attention to themselves for the purpose of making a career out of their time in office, and whether they are using "science" or "family values" or "ecological disaster" to help themselves, make no mistake: they care little for the truth.
The news media are more than happy to jump in and fan the flames, because that's how they make their living.
The "actual climate change pronouncements by scientists" are, by and large, pronouncements by politicians and news and pundits, most of whom have a bias for something other than science, such as the bias for the energy industry by politicians from oil and natural gas and coal states. This isn't intrinsically bad, but must be accounted for in public discourse. What is inexcusable is lies about scientific research, which industry is known for. See: the tobacco industry. See: Volkswagen regarding their vehicle emissions compliance.
"Science", done correctly, is investigation of hypotheses, (and on toward confirmation or rejection of those hypotheses) and cares little about political results. Scientists, of course, are human and may say things like this cartoon presents, even falsely, but that doesn't mean all of science is untrustworthy. The Spanish Inquisition doesn't nullify the primary message of Christianity; Richard Nixon's failure did not negate the Republican Party's tenets. It is not a falsification of science that there are changes in the conclusions drawn from one study to the next, because scientific discovery is not static. People thought the Earth was the center of the universe, then scientists found out it isn't. "Doctors" thought disease was caused by unbalanced bodily "humours", then scientists discovered bacteria and viruses.
Science done correctly is messy, uncertain, changeable. Politicians and news purveyors want absolutes, and that's really not science. Eco-warriors and energy corporations also want "their" truth accepted for opposite reasons, and for opposite results. Meanwhile, one disproven study (one!) connects autism and vaccines and some people are sure the science is "settled" in that case. Why trouble with science when a celebrity "knows the truth?"
Another politicization of science is the substitution of "climate change" for "global warming," instead of substituting "human-caused global warming" (aka, anthropogenic global warming) because that's what we're really talking about. It's been done in part because "global warming" sometimes doesn't look global in particular locations. Many know about the "Medieval Warm Period" from about 950 to 1250 A.D. What is not so well known is that while glaciers around the world have yielded evidence of retreating during that time, one area in the Andes Mountain Range had glaciers that advanced. Why? Most likely, the warm period resulted in increased snowfall over those watersheds, which causes glaciers to advance, if temperatures are fairly similar to before. So in addition to a general warming that changed Europe geopolitically and ethnically (see "Vikings") there may have been increased rainfall in some places, in contrast to the known decrease in rainfall that accompanied the increase in temperatures in the American Southwest, which caused a change in the dynamics of the ancient peoples who had lived there for so long. You can thank this period for Mesa Verde, so to speak.
As previously stated, climate change is proven and irrefutable. You can even stand in Central Park and see outcroppings with gouges left by ice sheets thousands of years ago. Likewise, "interglacial period global warming" is real, or there would still be ice sheets on top of Manhattan and Omaha. The debate is about man's role in the now measurable acceleration of global warming. Make no mistake, we are warmer, measurably, than our Grandparents were when they were kids at the turn of the 20th century, warmer than their Grandparents were, and especially warmer than their Grandparents were. There is also the need to separate "weather" and "climate." One extra hot summer does not confirm warming, as one extra frigid winter does not refute it. Even a difference over 100 years does not prove or disprove, which is why scientists are drilling ice cores in Greenland and the Antarctic, and seafloor cores around the globe. It's why many geologists specialize in looking for indicators of past climate in rocks and in fossils - to look even further back.
The climate record, along with modern remote sensing (NASA's satellite data over several decades), and even observations that we in the general public can make with our own eyes (visit Glacier National Park and see for yourself the extraordinary reduction in size of the glaciers for which the park is named in one century). All of these together require serious scientific investigation into the effects on the human population, and to determine if there is anything we can and must do to slow or stop it. There will be another ice age soon enough, in a geological time frame, but we won't have to worry about that for uncountable generations. In the meantime, rising sea levels will be moving a lot of people inland around the world. There is no way to fake the increases in flooding disasters that are videoed and reported many American coastal communities. They're not getting any better.