This will likely be true for the 2005 calendar year as well, as suggested by NASA, because differences between meteorological year and calendar year are usually extremely small.

However, because of the errors that accompany the observations, 2005 may have tied 1998 for the hottest year.

Nevertheless, whether 2005 is tied for the hottest (equaling 1998) or comes in second behind 1998, but ahead of 2004, which was ahead of 2003, which was ahead of 2002…. the picture is the same, the planet is getting hotter.

It is particularly significant that 2005 is tied with 1998 for the hottest year because 1998 was an El Niño year, a condition that naturally makes the key parts of the planet warmer. 2005 was not a year with El Niño conditions so this high temperature was reached as part of an upward trajectory caused by increasing greenhouse gases, such as CO2, in the atmosphere due to the burning of fossil fuels.

In addition to NASA Goddard Institute for Space Study, two other climate monitoring organizations, the U.S. National Oceanic and Atmospheric Administration and the U.K. Meteorological Office, agree that 2005 is the hottest year on record for the Northern Hemisphere, at roughly 0.72 degrees C (1.3 degrees Fahrenheit) above the historical average.
Whether 2005 has been the hottest year, is tied for the hottest year, or is the second hottest year, the problem is still the same – the planet is heating up.
Sources of disagreement
From the following article: The heat was on in 2005
Robert Henson, Nature 438, 1062 (22 December 2005) doi:10.1038/4381062a

"There are three teams that rank global temperatures. Their results vary mainly because of differences in how they combine data sets.

Each group draws on a different mix of the planet's land-based temperature stations to construct a temperature record. The University of East Anglia's Climatic Research Unit (CRU) uses about 4,200 stations worldwide; the National Oceanic and Atmospheric Administration (NOAA) uses 7,200 and NASA uses 6,000.

They also differ in how they analyse this information. NASA and NOAA pool their data, weighted by area, across the globe. But the Northern Hemisphere has much more land than the Southern: "We think this adds a northern bias," says Philip Jones of the CRU. His team averages the data for each hemisphere, then combines them. Another difference is that NASA calculates its temperature differences using a 1951–80 base period; the others use 1961–90.

But overall, the results are more alike than they are different. The three groups report similar rates of warming over land in the past century, according to a recent analysis by NOAA's Russell Vose.

Adding measurements from the ocean brings more uncertainty. For decades, scientists relied on fairly crude sea-surface-temperature measurements collected by ships through buckets and engine intakes. But by the early 11000s, sea-surface data from ships and buoys became more widely available, as did air temperatures construed from satellite data.

NOAA and NASA use an index that includes all these ocean sources; the CRU and the Hadley Centre for Climate Prediction and Research in Exeter, UK, rely on ship and buoy data. There is no consistent difference in the results, says Hadley's John Kennedy, but this year the CRU/Hadley index pegs ocean temperatures as being cooler than they were in 1998. That may be why that team seems likely to place global air temperatures short of the 1998 record."