Arctic sea ice has been tracked since 1979 by U.S. government satellites and shows a steady decline during more than three decades. A proposed thesis statement addressing this topic might be "Global warming and arctic sea ice trends are strongly linked with mounting evidence man-made pollutants are at least partially to blame".
Hard data from around the world shows the majority of the earth's glaciers shrinking over the past 100 years. There's a lively dialogue continuing between those who say it's caused by man-made climate change, and those insisting it's a result of drier weather patterns. A statement outlining this topic could read as "Glacial retreat and climate change is a contested issue in the popular literature, but the scientific data shows an undeniable relationship between them".
There's little debate within the climate and weather community that the earth has warmed since 1860. What's hotly debated is why these higher temperatures are happening. The majority of scientists with credible knowledge of physics or meteorology attribute at least a portion of it to human-produced industrial emissions. A proposed thesis statement addressing this issue is "An examination of the links between human activity and global temperature trends suggests a clear cause-and-effect relationship".
National Hurricane Center data shows a clear trend of increased hurricane frequency in the Atlantic Basin since the mid 1990s and this has been linked to human-induced climate change in the media. The body of evidence points to a natural oceanic cycle as the primary cause. A solid thesis statement expressing this idea might be "Hurricane increases in the Atlantic Basin since the mid 1990s are probably not the result of global warming".
Not only is arctic sea ice retreating, but so is land-based ice on the immense Greenland ice cap. This is a different topic than arctic sea ice as the data and research is in a whole different direction. Whereas sea ice is tracked by submarines and satellites, land-based ice relies on ice cores and pollen analysis. The case with Greenland would make a fine thesis as the data shows both growth and shrinkage in different regions of the cap during the past 50 years. A potential thesis statement is "The Greenland ice cap is both shrinking and expanding, and climate change can be linked to both trends".