Misinformation online remains a big problem, especially immediately after big news lands. Unscrupulous folks can and do spread outright falsehoods, and not all sources meet the same standards of fact-checking or trustworthiness. In its ongoing efforts to bring you reliable and relevant information, Google Search is rolling out a new notice for "rapidly evolving" subjects, so you know to check back in later once the facts have settled.
When big news lands and we haven't seen a story about it, most of us Google up related keywords to try to track down some facts about the story. Given enough time, the best sources of information have a tendency to rise to the top of those results, but that isn't instantaneous, and in the first minutes to hours following an event, you might not see the most reliable coverage highlighted in Search.
The new change doesn't interfere with results at all, but it does preface them with a warning as in the example provided by Google just above, stating "it looks like these results are changing quickly" and further explaining, "if this topic is new, it can sometimes take time for results to be added by reliable sources."
This follows other recent efforts by Google to increase the quality and understanding of news and search results. Earlier this year, Google rolled out a new "about this result" card that describes a given source based on its Wikipedia entry. That way, if you aren't familiar with a given site, you can see if it's some fly-by-night venue or a trustworthy source of reporting and information. Google also brought its Full Coverage feature to Search to help show multiple sources and perspectives for a given story, and give you an idea for how the facts and reporting may have changed over time.
The new disclaimer in search results are rolling out in English in the US to start, with a wider expansion and other features set to arrive "over the coming months."