Not with a direct command afaik.
You have to edit the config.xml file.
I normally do that via a SSH connection and the Posh-Ssh module, with a sed command.
This changes the loglevel from warning to error.
$esxName = 'MyEsx'
$cred = Get-Credential -Message "SSH crdentials for ESXi node $esxName"
$session = New-SSHSession -ComputerName $esxName -Credential $cred –AcceptKey
$result = Invoke-SSHCommand -SSHSession $session -Command $cmdSub
Remove-SSHSession -SSHSession $session | Out-Null
.
Blog: lucd.info Twitter: @LucD22 Co-author PowerCLI Reference