After adjusting for scientists data adjustment, it cannot be said that it is the warmest period.

In 2017, a peer reviewed study found that climate scientists were adjusting temperatures prior to 1960 colder than they most likely were, increasing the warming trend, making it impossible to determine if recent years have been the warmest ever.
The study examined the EPA’s GHG/CO2 Endangerment Finding's 3 lines of evidence in favor of a warming trend and found that each new version of their data shows a steeper linear warming trend than the one before it over it's entire history. They also found that they almost always removed cyclical patterns (fluctuations) in temperature. They tried to validate Global average surface temperature (GAST) data appon which the EPA's GHG/CO2 Endangerment Finding is based using relevant data, such as the best doccumented and understood data from the US and other countries and global satellite data, which provide much greater coverage of the earth's temperatures and are not effected by contamination from heat leakage from cities. They concluded that GAST data is inconclusive and therefore it cannot be said that recent years are the warmest ever, as claimed by the EPA. https://thsresearch.files.wordpress.com/2017/05/ef-gast-data-research-report-062717.pdf